astro glossary

Mariner 1

first Mariner launch. It was intended to fly by Venus. The spacecraft was launched on July 22, 1962, but was destroyed approximately 5 minutes after liftoff by the Air Force Range Safety Officer when its malfunctioning Atlas-Agena rocket went off course.

Gemini 3

first crewed Earth-orbiting spacecraft of the Gemini series. It was piloted by Gus Grisson and John Young in 1965.

Apollo 7

first manned Apollo flight, and first manned flight of the Saturn IB booster rocket.

Apollo 1

first manned Apollo mission (1967). Astronauts Gus Grissom, Edward White, and Roger Chaffee were killed when a fire erupted in their Apollo spacecraft during a test on the launch pad. The spacecraft never launched.

Aqua

part of the EOS program, and launched in 2002, Aqua carries six state-of-the-art instruments to observe the Earth's oceans, atmosphere, land, ice and snow covers, and vegetation, providing high measurement accuracy, spatial detail, and temporal frequency. This comprehensive approach to data collection enables scientists to study the interactions among the four spheres of the Earth system--the oceans, land, atmosphere, and biosphere. Aqua, as well as the Terra satellite, carries the MODIS imaging instrument. The National Space Development Agency of Japan's Advanced Microwave Scanning Radiometer - EOS (AMSR-E) is one of six key Earth-observing instruments on board Aqua and has recently been used to obtain images of the sea ice covers of both polar regions, showing their changes from the June 2-4 period to the July 21-22 period. In these images, white indicates the area of sea ice cover and gray indicates land. Because of the time period covered (late spring to summer in the Northern Hemisphere; late fall to winter in the Southern Hemisphere), the area of the ice cover in the Arctic region is decreasing while the area of ice cover in the Antarctic region is increasing, a fact captured very well in these images. Aqua, Latin for "water," is named for the large amount of information that the Aqua spacecraft will collect about the Earth's water cycle. In particular, the Aqua data will include information on water vapor and clouds in the atmosphere, precipitation from the atmosphere, soil wetness on the land, glacial ice on the land, sea ice in the oceans, snow cover on both land and sea ice, and surface waters throughout the world's oceans, bays, and lakes. Such information will help scientists improve the quantification of the global water cycle and examine such issues as whether or not the cycling of water might be accelerating

Gemini 12

tenth and final flight of the Gemini series.

Gemini 8

performed the first docking to ever take place in space, between Gemini 8 and the Gemini Agena Target Vehicle (GATV), which was uncrewed and launched earlier in the day. It carried two astronauts (as all Gemini missions did), Neil Armstrong and David Scott.

The Pointers

Dubhe (Alpha Ursae Majoris) and Merak (Beta Ursae Majoris), which point to Polaris. Dubhe and Merak are the two stars at the end of the cup in the Big Dipper. In the Southern Hemisphere, the Pointers are Alpha and Beta Centauri, which point to the Southern Cross.

Oort, Jan

Dutch astronomer whose hypothesis that the comets have a common origin, postulated in 1950, was later proven to be correct. The Oort cloud of comets, where long-period comets originate, bears his name.

Adams, John

English astronomer credited with the mathematical discovery of Neptune by investigating irregularities in the orbit of Uranus.

Gran Telescopio Canarias (GTC, or Great Telescope Canary Islands) -

a 10.4 m reflecting telescope on the island of La Palma (Canary Islands), Spain. Its primary mirror is composed of 36 hexagonal segments that work together as a single piece of reflective glass. It is similar in construction to the twin Keck 1 and Keck 2 telescopes on Mauna Kea Hawaii, but with a slightly larger mirror. It is the second largest reflecting telescope in the world, after the LBT (although the LBT has two mirrors on a single mount, whereas the GTC has a single primary).

Progress

a Russian expendable freighter spacecraft. The spacecraft is an unmanned resupply spacecraft during its flight but upon docking with a space station it allows astronauts inside, hence it is classified manned by the manufacturer. It was derived from the Soyuz spacecraft, and is launched with the Soyuz launch vehicle. It is currently used to supply the International Space Station, but was originally used to supply Soviet space stations for many years. There are three to four flights of the Progress spacecraft to the ISS per year. Each spacecraft remains docked until shortly before the new one, or a Soyuz (which uses the same docking ports) arrives. Then it is filled with waste, disconnected, deorbited, and destroyed in the atmosphere.

galactic chimney

a cavity in the interstellar medium, created by multiple supernova explosions, that can act as a conduit for the efficient transport of hot gas from a galaxy's disk to its halo.

bolide

a term synonymous with 'fireball'. It is usually used among geologists rather than astronomers, and it means a very large impactor whose nature is unknown.

flare star

a type of variable star that is a red dwarf that shows rapid and irregular changes in brightness.

EOS (Earth Observing System)

program consisting of a series of spaceborne satellite instruments to monitor crucial components of the Earth system, an advanced data handling system, and teams of scientists who will evaluate on-going climate change and predict future changes. Ultimately, EOS will produce scientifically sound recommendations for environmental policy to national and international bodies to mitigate or prepare for these changes.

Gemini

program that bridged the gap between the Mercury and Apollo programs. The Gemini program had 4 objectives: 1) To subject astronauts to long duration flights- a requirement for projected later trips to the moon or deeper space; 2) to develop effective methods of rendezvous and docking with other orbiting vehicles, and to maneuver the docked vehicles in space; 3) to perfect methods of reentry and landing the spacecraft at a pre-selected land-landing point; 4) to gain additional information concerning the effects of weightlessness on crew members and to record the physiological reactions of crew members during long duration flights.

However, this value is expected to change once the comet warms up further and ice grains

rather than pure dust grains - are ejected from the surface.

Venera 13

returned the first color images of Venus' surface and discovered basalt in a soil sample using a spectrometer.

gravitational waves

ripples in the overall geometry of space produced by the acceleration of moving objects.

Zeeman effect

spectral line splitting due to the influence of magnetic fields.

elongation

the angle an inferior planet makes with the Sun as seen from the earth.

Egyptians

developed and implemented the first solar calendar.

Foucault pendulum

device that first proved that the Earth rotates on its axis.

Vostok-1

Soviet spacecraft that carried the first man, Yuri Gagarin, into space. Launch and landing occurred on April 12, 1961, with a total duration of 1 hour 48 minutes.

Soyuz 19

Soviet spacecraft that docked with an American Apollo spacecraft during the Apollo-Soyuz Test Project mission in July, 1975.

Apollo 13

unlucky spacecraft whose oxygen tank exploded en route, forcing the cancellation of its lunar landing. The astronaut team, commanded by Jim Lovell, did make adjustments and made it back safely to Earth. This was the only manned non-orbital lunar flight.

Halley, Edmond

English astronomer who identified his namesake comet with a period of 76 years. Compiled a star catalogue, detected proper motion of stars, and started research on the AU. He also helped his friend Isaac Newton publish his Principia (he financed Newton's work) and was a pioneer geophysicist and meteorologist. He was the first to propose that nebulas were clouds of interstellar gas in which stars were being formed. He became the second Astronomer Royal (of England) in 1720 (Flamsteed was the first).

Keck Interferometer

- At 4,150 meters (13,600 feet) above the Pacific Ocean, atop the dormant volcano Mauna Kea on the "Big Island" of Hawaii, the twin Keck Telescopes are the world's largest telescopes for optical and near-infrared astronomy. The Keck Interferometer joins these giant telescopes to form a powerful astronomical instrument. At the heart of each Keck Telescope is a revolutionary primary mirror. Ten meters in diameter, the mirror is composed of 36 hexagonal segments that work in concert as a single piece of reflective glass. The 85-metre (280 ft) separation between the two telescopes gives them the effective angular resolution in one direction of an 85-metre (280 ft) mirror. The lack of additional outrigger telescopes makes the Keck Interferometer unsuitable for interferometric imaging, so work has concentrated on nulling interferometry and angular diameter measurements instead.

Kepler, Johannes

- German mathematician, astronomer and astrologer, and key figure in the 17th century Scientific revolution. He is best known for his eponymous laws of planetary motion, codified by later astronomers based on his works Astronomia nova, Harmonices Mundi, and Epitome of Copernican Astrononomy. They also provided one of the foundations for Isaac Newton's theory of universal gravitation. Kepler's three laws of planetary motion are: 1) the orbit of each planet is an ellipse with the sun one of the foci. 2) The radius vector of each planet sweeps out equal areas in equal times, and 3) the period of a planet squared is proportional to its mean distance from the sun. He worked as an assistant to Tycho Brahe in 1600, gaining access to data Tycho's data on the motion of Mars, which allowed Kepler to derive his laws.

Jansky, Karl

- Radio engineer who, while using a short-wave radio receiver with a directional antenna, noticed a background hiss that rose to a peak every 24 hours. He assumed, correctly, that this was due to Earth's rotation and that the signal was coming from outer space. He localized the source to the constellation of Sagittarius, near the center of the Milky Way. This was the beginning of radio astronomy. The unit of radio emission strength, the jansky, was named after him.

LZT (Large Zenith Telescope)

- a 6.0 m diameter liquid mirror telescope located in the University of British Columbia's Malcolm Knapp Research Forest, about 70km east of Vancouver, Canada. It is one of the largest optical telescopes in the world, but still quite inexpensive. While a zenith telescope has the obvious disadvantage of not being able to look anywhere but a small spot straight up, its simplified setup permits the use of a mirror consisting of a smoothly spinning pan filled with liquid mercury. Such a mirror can be made much larger than a conventional mirror, greatly increasing light collecting ability. The LZT is used for transit imaging, meaning that earth's rotation moves stars along the sensor, and the latent image in the sensor is moved electronically in step with this movement and read out at the trailing edge.

Le Verrier, Urbain

- a French mathematician who specialized in celestial mechanics and is best known for his part in the discovery of Neptune. Le Verrier's most famous achievement is his prediction of the existence of the then unknown planet Neptune, using only mathematics and astronomical observations of the known planet Uranus. Le Verrier was intensely engaged for months in complex calculations to explain small but systematic discrepancies between Uranus's observed orbit and the one predicted from the laws of gravity of Newton. At the same time, but unknown to Le Verrier, similar calculations were made by John Couch Adams in England. Le Verrier announced his final predicted position for Uranus's unseen perturbing planet publicly to the French Academy on August 31, 1846, two days before Adams's final solution, which turned out to be 12° off the mark, was privately mailed to the Royal Greenwich Observatory. There was, and to an extent still is, controversy over the apportionment of credit for the discovery. There is no ambiguity to the discovery claims of Le Verrier, Galle, and d'Arrest. Adams's work was begun earlier than Le Verrier's but was finished later and was unrelated to the actual discovery. Not even the briefest account of Adams's predicted orbital elements was published until more than a month after Berlin's visual confirmation. But Adams himself made full public acknowledgement of Le Verrier's priority and credit (not forgetting to mention the role of Galle) when he gave his paper to the Royal Astronomical Society in November 1846.

Kitt Peak National Observatory

- a United States astronomical observatory located on a 2,096 m (6,880 ft) peak in the Arizona-Sonoran Desert 88 kilometers (55 miles) southwest of Tucson. With 23 telescopes, it is the largest, most diverse gathering of astronomical instruments in the world. The McMath-Pierce Solar Telescope located on the facilities is the largest solar telescope in the world, and the largest unobstructed reflector (it doesn't have a secondary mirror in the path of incoming light). Kitt Peak is also famous for hosting the first telescope (an old 91 cm reflector) used to search for near-Earth asteroids, and calculating the probability of an impact with planet Earth.

Bishop's Ring

- a diffuse brown or bluish halo observed around the sun in the presence of large amounts of dust in the stratosphere. It is typically observed after large volcanic eruptions. The first recorded observation of a Bishop's Ring was by Rev. S. Bishop of Honolulu, after the Krakatoa eruption of 1883. Most observations agree that the inner rim of the ring is whitish or bluish white and that its outside is reddish, brownish or purple. The area enclosed by the ring is significantly brighter than its surroundings. From the sequence of colors with the red on the outside one can conclude that the phenomenon is caused by diffraction because halos always have their red part on their inside. In average, the radius of the ring is about 28°. This is a rather big radius which can only be caused by very small dust particles (0,002 mm) which all have to be of about the same size.

LIGO (Large Interferometer Gravitational-Wave Observatory)

- a facility dedicated to the detection of cosmic gravitational waves and the harnessing of these waves for scientific research. It consists of two widely separated installations within the United States — one in Hanford Washington and the other in Livingston, Louisiana — operated in unison as a single observatory. At least two detectors located at widely separated sites are essential for the unequivocal detection of gravitational waves. Local phenomena such as micro-earthquakes, acoustic noise, and laser fluctuations can cause a disturbance at one site, simulating a gravitational wave event, but such disturbances are unlikely to happen simultaneously at widely separated sites. After a nationwide open competition, NSF selected sites near Livingston, Louisiana, and at Hanford, Washington, for the LIGO installations. The sites, which are separated by nearly 2,000 miles, are both flat and large enough to accommodate the 4-kilometer interferometer arms. Both are also far enough from urban development to ensure that they are seismically and acoustically quiet, but still within convenient distance of housing for resident and visiting staff. Gravitational waves are ripples in the fabric of space and time produced by violent events in the distant universe, for example by the collision of two black holes or by the cores of supernova explosions. Gravitational waves are emitted by accelerating masses much as electromagnetic waves are produced by accelerating charges. These ripples in the space-time fabric travel to Earth, bringing with them information about their violent origins and about the nature of gravity. Albert Einstein predicted the existence of these gravitational waves in 1916 in his general theory of relativity, but only since the 1990s has technology become powerful enough to permit detecting them and harnessing them for science. Although they have not yet been detected directly, the influence of gravitational waves on a binary pulsar (two neutron stars orbiting each other) has been measured accurately and is in good agreement with the predictions. Scientists therefore have great confidence that gravitational waves exist. Joseph Taylor and Russel Hulse were awarded the 1993 Nobel Prize in Physics for their discovery of this binary pulsar.

MACHO (Massive Compact Halo Object)

- a general name for any kind of astronomical body that might explain the apparent presence of dark matter in galaxy halos. A MACHO is a small chunk of normal baryonic matter, which emits little or no radiation and drifts through interstellar space unassociated with any solar system. Since MACHOs would not emit any light of their own, they would be very hard to detect. MACHOs may sometimes be black holes or neutron stars as well as brown dwarfs or unassociated planets. White dwarfs and very faint red dwarfs have also been proposed as candidate MACHOs. The term was chosen whimsically, by contrast with WIMP, another proposed form of dark matter.

Cernan, Eugene

astronaut who drove the Lunar Rover during the Apollo 17 mission to the Moon. He has a space center named after him at Triton College.

Bluford, Guion

first African American in space, aboard the Space Shuttle Challenger in 1983.

Armstrong, Neil

the first human to set foot on the Moon (Apollo 11 mission, July 20, 1969). Buzz Aldrin followed Armstrong onto the surface, while Michael Collins remained in orbit in the Command Module.

Ice Cube

the largest neutrino detector in the world. The sensors are buried 1,450 to 2,450 m below the surface of the Antarctic ice, and the detectors encompass a volume of more than 3,000 million tons of ice. It can detect extraterrestrial neutrinos with energies of more than 100 GeV. Neutrinos are not affected by magnetic fields, and most of the time they pass through whatever is in their way. That's why they're so hard to detect. Most of them pass right through the Earth without being detected. But neutrinos do sometimes interact with ice and spark a tiny flash of detectable light. The Ice Cube uses a cubic kilometer of clear Antarctic ice cap outfitted with light detectors.

LOFAR (Low Frequency Array)

- a project to build an interferometric array of radio telescopes distributed across the Netherlands, with at least five stations in Germany one station in Great Britain, France and Sweden, and possibly in other European countries such as Poland and Ukraine, with a total effective collecting area of up to 1 square kilometre. The processing of the data is done by a Blue Gene/P supercomputer situated at the University of Groningen. LOFAR started as a new and innovative effort to force a breakthrough in sensitivity for astronomical observations at radio-frequencies below 250 MHz. The basic technology of radio telescopes had not changed since the 1960's: large mechanical dish antennas collect signals before a receiver detects and analyses them. Half the cost of these telescopes lies in the steel and moving structure. A telescope 100x larger than existing instruments would therefore be unaffordable. New technology was required to make the next step in sensitivity needed to unravel the secrets of the early universe and the physical processes in the centers of active galactic nuclei. LOFAR is the first telescope of this new sort, using an array of simple omni-directional antennas instead of mechanical signal processing with a dish antenna. The electronic signals from the antennas are digitised, transported to a central digital processor, and combined in software to emulate a conventional antenna. The cost is dominated by the cost of electronics and will follow Moore's law, becoming cheaper with time and allowing increasingly large telescopes to be built. So LOFAR is an IT-telescope. The antennas are simple enough but there are a lot of them - 25000 in the full LOFAR design. To make radio pictures of the sky with adequate sharpness, these antennas are to be arranged in clusters that are spread out over an area of ultimately 350 km in diameter.

Arecibo Observatory

- a very sensitive radio telescope located approximately 9 miles (14 km) south-southwest from the city of Arecibo in Puerto Rico. It is operated by Cornell University under cooperative agreement with the National Science Foundation. The observatory works as the National Astronomy and Ionosphere Center (NAIC) although both names are officially used to refer to it. NAIC more properly refers to the organization that runs both the observatory and associated offices at Cornell University. The observatory's 305 m radio telescope is the largest single-aperture telescope ever constructed. It carries out three major areas of research: radio astronomy, aeronomy (using both the 305 m telescope and the observatory's lidar facility), and radar astronomy observations of solar system objects. Usage of the telescope is gained by submitting proposals to the observatory, which are evaluated by an independent board of referees.

Hoyle, Fred

- an English astronomer noted primarily for the theory of stellar nucleosynthesis and his often controversial stances on other cosmological and scientific matters—in particular his rejection of the "Big Bang" theory, a derisive term originally coined by him on BBC radio.

CARMA (Combined Array for Research in Millimeter-wave Astronomy)

- an astronomical instrument comprising 23 radio telescopes in the Owens Valley, California. These telescopes form an astronomical interferometer where all the signals are combined in a purpose-built computer (a correlator) to produce high-resolution astronomical images. Until the Atacama Large Millimeter Array is constructed in Chile, this instrument will be the most powerful millimeter wave interferometer in the world. This array is unique for being a heterogeneous collection of radio telescopes of varying sizes and design. There are three types of telescopes, all Cassegrain reflector antennas with parabolic primary mirrors and hyperbolic secondary mirrors.

ALMA (Atacama Large Millimeter/submillimeter Array)

- an international astronomy project that consists of an astronomical interferometer formed from an array of radio telescopes, located at Llano de Chajnantor Observatory in the Atacama desert in northern Chile. The telescope is expected to revolutionize modern astronomy by providing an insight on star formation in the early universe and imaging local star and planet formation in great detail. With a cost in excess of one billion US dollars, it is the most ambitious ground-based telescope currently under construction (to be completed in 2012). The array will have much higher sensitivity and higher resolution than existing sub-millimeter telescopes such as the single-dish James Clerk Maxwell Telescope or existing interferometer networks such as the Submillimeter Array or the IRAM Plateau de Bure facility. By moving the antennas at regular intervals, the resolution of the array and the size of object that can be imaged will be altered, producing a "zoom-lens" capability, similar to that employed at the VLA site in New Mexico. The high sensitivity is mainly achieved through the large numbers of telescopes that will make up the array. The telescope will have a spatial resolution of 10 milliarcseconds, 10 times better than the Very Large Array (VLA) and the Hubble Space Telescope.

CHARA (The Center for High Angular Resolution Astronomy) Array

- an optical astronomical interferometer operated by The Center for High Angular Resolution Astronomy (CHARA) of the Georgia State University (GSU). CHARA is the World's highest angular resolution telescope at near-infrared wavelengths. It is located at the Mount Wilson Observatory, near Los Angeles, California. The CHARA Array is an interferometer formed from six 1 meter (40-inch) telescopes arranged along three axes with a maximum separation length of 330 m. The light beams travel through vacuum tubes and are combined optically, requiring a building 100 meters long with movable mirrors to keep the light in phase as the earth rotates. CHARA began scientific use in 2002 and began "routine operations" in early 2004. In the infrared, the array has an interferometric imaging resolution of 0.0005 arcseconds. All six telescopes are in regular use for scientific observations and as of late 2005 imaging results are routinely acquired. The array captured the first image of the surface of a main sequence star other than the sun published in early 2007.

ATA (Allen Telescope Array)

- formerly known as the One Hectare Telescope (1hT), is a joint effort by the SETI Institute and the Radio Astronomy Laboratory (RAL) at the University of California, Berkeley to construct a radio interferometer that is dedicated to astronomical observations and a simultaneous search for extra-terrestrial intelligence. The ATA is under construction at the Hat Creek Radio Observatory, 290 miles northeast of San Francisco, California. When completed, the array is expected to consist of 350 antennas. The first phase with 42 antennas is complete and became operational in 2007. The ATA will be a centimeter-wave array that pioneers the Large-Number Small-Diameter (LNSD) concept of building radio telescopes. Compared to a large dish antenna, large numbers of smaller dishes are cheaper for the same collecting area. However, to get similar sensitivity, the signals from all telescopes must be combined. This requires high performance electronics, and has been impractically expensive until now. The ATA has four primary advantages for scientific studies over all major radio telescopes built to date: a very wide field of view (2.45° at λ = 21 cm), complete instantaneous frequency coverage from 0.5 to 11.2 GHz, multiple simultaneous backends, and active interference mitigation. The instantaneous area of sky imaged is 17 times that of the Very Large Array (VLA). The instantaneous frequency coverage of more than 4 octaves is unprecedented in radio astronomy and is the result of a unique feed, input amplifier, and signal path design. Active interference mitigation will make it possible to observe even at the frequencies of many terrestrial radio emitters. The new array concept is named the "Allen Telescope Array" (ATA) (formerly, One Hectare Telescope [1HT]) after the project's benefactor Paul Allen (one of the co-founders of Microsoft).

Olbers' paradox

- paradox that asks why the sky is not ablaze with starlight if the universe is infinite in extent and uniformly filled with stars? To answer why the sky is dark at night, given that the universe appears to be homogeneous and isotropic (the same in all directions), one or both of the other two assumptions must be false. Either the universe is finite in extent, or it evolves over time. In fact, the answer involves aspects of each and is intimately tied to the behavior of the universe on the largest scales. The universe, according to the mainstream theory of the universe, called the Big Bang Theory, is only finitely old; stars have existed only for part of that time. So, as Edgar Allan Poe suggested, the earth receives no starlight from beyond a certain distance. According to the Big Bang Theory, the sky was much brighter in the past, especially in the first few seconds of the universe. All points of the local sky at that era were therefore brighter than the circle of the sun, despite the finite and even more limited range that light could travel in that prehistoric era; this implies that most light rays will terminate not in a star but in the relic of the Big Bang. While the finite distance for the origin of any received light does not by itself solve the paradox, the Big Bang Theory also involves the expansion of the "fabric" of space itself (not just the distance of objects in that space) that can cause the energy of emitted light to be reduced via redshift. More specifically, the extreme levels of radiation from the Big Bang have been redshifted to microwave wavelengths as a result of the cosmic expansion, and thus form the cosmic microwave background radiation. This explains the relatively low light densities present in most of our sky despite the assumed bright nature of the Big Bang. The redshift also affects light from distant stars and quasars, but the diminution is only an order of magnitude or so, since the most distant galaxies and quasars have redshifts of only around 5. Thus, the mainstream explanation of Olbers' paradox requires a universe that is both finitely old and expanding.

LMT (Large Millimeter Telescope)

- the world's largest and most sensitive single-aperture telescope in its frequency range, built for observing radio waves in the wave lengths from approximately 0.85 to 4 mm. It has an active surface with a diameter of 50 meters and 2000 m² of collecting area. It is located on top of the Sierra Negra, the fifth highest peak in Mexico. Millimeter wavelength observations using the LMT will give astronomers a view of regions which are obscured by dust in the interstellar medium, thus increasing our knowledge about star formation. The telescope is also particularly fitted for observing solar system planetesimals and planets and extra-solar protoplanetary disks which are relatively cold and emit most of their radiation at millimeter wavelengths.

Brahe, Tycho

Danish astronomer Tycho is credited with the most accurate astronomical observations of his time, and the data was used by his assistant Kepler to derive the laws of planetary motion. No one before Tycho had attempted to make so many redundant observations, and the mathematical tools to take advantage of them had not yet been developed. He did what others before him were unable or unwilling to do - to catalogue the planets and stars with enough accuracy to determine whether the Ptolemaic or Copernican system was more valid in describing the heavens. He discovered a supernova in 1572 and observed comets in 1577, proving that they were in an orbit among planets. He also concluded that a comet's orbit must be elongated, which conflicted the belief in planetary spheres. He determined the length of a year to within a second necessitating a calendar reform in 1582. He founded an island astronomical institute called Uraniborg. While a student in Germany, he lost part of his nose in a sword duel. For the rest of his life, he was said to have worn a realistic replacement made of silver and gold, using a paste to keep it attached.

Hawking, Stephen

English physicist who discovered that the surface area at the event horizon of a black hole could never decrease, but later found a loophole that if an electron-positron pair formed just outside the radius then one would fall in and the other could escape as Hawking radiation. He is well-known for positing singularities, regions at the center of black holes with infinite mass, causing the laws of physics to break down. He became Lucasian professor of mathematics at Cambridge in 1979 (the same position held by Newton).

Herschel, William

German-born English astronomer and composer who became famous for discovering Uranus. He also discovered infrared radiation. Herschel discovered two moons of Saturn, Mimas and Enceladus; as well as two moons of Uranus, Titania and Oberon. During the course of his career, he constructed more than four hundred telescopes. He worked on creating an extensive catalogue of nebulae. He continued to work on double stars, and was the first to discover that most double stars are not mere optical doubles as had been supposed previously, but are true binary stars, thus providing the first evidence that Newton's laws of gravitation apply outside the solar system. From studying the proper motion of stars, he was the first to realize that the solar system is moving through space, and he determined the approximate direction of that movement. He also studied the structure of the Milky Way and concluded that it was in the shape of a disk.

Ptolemy

Greek/Roman astronomer and mathematician who attempted to adapt horoscopic astrology to the Aristotelian natural philosophy of his day. He wrote the Almagest, the only surviving comprehensive ancient treatise on astronomy. Proposed a geocentric system with circular orbits in which he used epicycles around the deferent to explain apparent motions. The Almagest also contains a star catalogue, which is an appropriated version of a catalogue created by Hipparchus. Its list of forty-eight constellations is ancestral to the modern system of constellations, but unlike the modern system they did not cover the whole sky (only the sky Hipparchus could see). Through the Middle Ages it was spoken of as the authoritative text on astronomy, with its author becoming an almost mythical figure, called Ptolemy, King of Alexandria. The Almagest was preserved, like most of Classical Greek science, in Arabic manuscripts (hence its familiar name). Because of its reputation, it was widely sought and was translated twice into Latin in the 12th century, once in Sicily and again in Spain. Ptolemy's model, like those of his predecessors, was geocentric and was almost universally accepted until an equally systematic presentation of a heliocentric geometrical model by Nicolaus Copernicus.

Chandrasekhar, Subrahmanyan

Indian astronomer who investigated transfer of energy in stellar atmosphere by radiation and convection. The Chandrasekhar limit limits the mass of bodies made from electron-degenerate matter, a dense form of matter which consists of nuclei immersed in a gas of electrons. The limit. The Chandrasekhar limit is the maximum mass of a white dwarf before it turns into a neutron star. This limit is the maximum non-rotating mass which can be supported against gravitational collapse by electron degeneracy pressure. Stars produce energy through nuclear fusion, producing heavier elements from lighter ones. The heat generated from these reactions prevents gravitational collapse of the star. Over time, the star builds up a central core which consists of elements which the temperature at the center of the star is not sufficient to fuse. For main-sequence stars with a mass below approximately 8 solar masses, the mass of this core will remain below the Chandrasekhar limit, and they will eventually lose mass (as planetary nebulae) until only the core, which becomes a white dwarf, remains. Stars with higher mass will develop a degenerate core whose mass will grow until it exceeds the limit. At this point the star will explode in a core-collapse supernova, leaving behind either a neutron star or a black hole.

Galileo

Italian astronomer who developed the astronomical telescope and was first to see sunspots, the 4 main satellites of Jupiter and Venus going through its phases. He also discovered that freely falling bodies have the same constant acceleration, and that a body moving on a perfectly smooth horizontal surface would neither speed up nor slow down. He invented the thermometer and hydrostatic balance, and discovered that the path of a projectile is a parabola. Galileo's championing of Copernicanism was controversial within his lifetime. The geocentric view had been dominant since the time of Aristotle, and the controversy engendered by Galileo's presentation of heliocentrism as proven fact resulted in the Catholic Church's prohibiting its advocacy as empirically proven fact, because it was not empirically proven at the time and was contrary to the literal meaning of Scripture. Galileo was eventually forced to recant his heliocentrism and spent the last years of his life under house arrest on orders of the Roman Inquisition.

Grimaldi, Francesco

Italian scientist who discovered that light was deviated at the edge of an obstacle in its path (diffraction). Later physicists used his work as evidence that light was a wave, and Isaac Newton used it to arrive at his more comprehensive theory of light. He originated the tradition of naming the Moon's features after famous scientists. He built and used instruments to measure geological features on the Moon, and drew an accurate map or selenograph, which was published by Riccioli.

Zwicky, Fritz

Swiss astronomer Zwicky pioneered and promoted the use of the first Schmidt telescopes used in a mountain-top observatory in 1935. He hand-carried the Schmidt lens from Germany, which had been polished by the optician, Bernard Schmidt. In 1934 he and Baade coined the term "supernova" and hypothesized that they were the transition of normal stars into neutron stars, as well as the origin of cosmic rays. It was a prescient insight that had tremendous impact in determining the size and age of the universe in subsequent decades. In support of this hypothesis, Zwicky started hunting for supernovae, and found a total of 120 by himself. While examining the Coma galaxy cluster in 1933, Zwicky was the first to use the virial theorem to infer the existence of unseen matter, what is now called dark matter.

aurora

a colorful light show near the magnetic poles of the earth, caused when particles escaping from the Van Allen belts escape from the magnetosphere and collide with air molecules. The colorful display results when atmospheric molecules, excited upon collision with the charged particles, fall back to their ground states and emit visible light. Many different colors are produced because each type of atom or molecule can take one of several possible paths as it returns to its ground state. In the north, the spectacle is called the aurora borealis, or northern lights. In the south, it is called the aurora australis, or southern lights.

cosmic rays

a major component of the interstellar media consisting of charged particles which have speeds close to that of light. They are energetic particles originating from space that impinge on Earth's atmosphere. Almost 90% of all the incoming cosmic ray particles are protons, about 9% are helium nuclei (alpha particles) and about 1% are electrons (beta minus particles). The term "ray" is a misnomer, as cosmic particles arrive individually, not in the form of a ray or beam of particles. The variety of particle energies reflects the wide variety of sources. The origins of these particles range from energetic processes on the Sun all the way to as yet unknown events in the farthest reaches of the visible universe. Cosmic rays can have energies of over 1020 eV, far higher than the 1012 to 1013 eV that man-made particle accelerators can produce.

Drake, Frank

astronomer who is most famous for founding SETI (the Search for Extra Terrestrial Intelligence) and creating the Drake equation and Arecibo Message. The Drake equation is an attempt to estimate the number of extraterrestrial civilizations in our galaxy with which we might come in contact. The equation has many variables. The Drake equation defines a set of concatenated probabilities to help set constraints on the number of intelligent civilizations ('N'), and to illustrate our true lack of information (based upon insuffient data) in the pursuit of this exploration. The outcome of such a "sensitivity" analysis reveals that 'N' lies between 1 and 1,000,000. In 1960 Drake conducted the first radio search for extraterrestrial intelligence, known as Project Ozma. After Ozma, he founded SETI to carry on this work.

Hubble, Edwin

astronomer who profoundly changed astronomers' understanding of the nature of the universe by demonstrating the existence of other galaxies besides the Milky Way. He also discovered that the degree of redshift observed in light coming from a galaxy increased in proportion to the distance of that galaxy from the Milky Way. This became known as Hubble's law, and would help establish that the universe is expanding. He discovered Cepheid variable in several spiral galaxies. Hubble also devised the most commonly used system for classifying galaxies, grouping them according to their appearance in photographic images. He arranged the different groups of galaxies in what became known as the Hubble sequence. The Hubble constant (H0) is the ratio of the velocity of galactic recession to distance. The currently accepted value of this constant is approximately 70.1 (km/s)/Mpc.

Kirkwood, Daniel

astronomer whose most significant contribution came from his study of asteroid orbits. When arranging the then-growing number of discovered asteroids by their distance from the Sun, he noted several gaps, now named Kirkwood gaps in his honor, and associated these gaps with orbital resonances with the orbit of Jupiter. These asteroid free zones in the solar system are at 2.5, 2.95 and 3.3 AU from the Sun. They exist because the effect of Jupiter's mass forces any asteroids into other orbits. Further, Kirkwood also suggested a similar dynamic was responsible for Cassini Division in Saturn's rings, as the result of a resonance with one of Saturn's moons. In the same paper, he was the first to correctly posit that the material in meteor showers is cometary debris.

Lovell, James

command module pilot of Apollo 8, the first orbit around the Moon. He also commanded Apollo 13, the mission that had to be aborted because of an explosion onboard.

Ride, Sally

first American woman in space, aboard the Space Shuttle Challenger in 1983.

LBT (Large Binocular Telescope)

located on Mount Graham in Arizona, the LBT is one of the world's highest resolution and most technologically advanced optical telescopes, capable of creating images in the near-infrared with 10 times the resolution of the Hubble Space Telescope. The telescope employs two 8.4 m (22 ft) primary mirrors mounted on a single base (hence the name 'binocular'). Its collecting area is equivalent to an 11.8 metres (39 ft) circular aperture, greater than any other single telescope. Also, an interferometric mode will be available, with a maximum baseline of 22.8 metres (75 ft) for aperture synthesis imaging observations and a baseline of 15 metres (49 ft) for nulling interferometry. Because it combines the beams from separate telescope mirrors according to a special optical concept (Fizeau combination) it will provide high-resolution images of faint objects over a wide field-of-view. Nulling techniques, taking advantage of the deformable secondary telescope mirror to correct for atmospheric turbulence, will enable the LBTI to study emissions from faint dust clouds around other stars. These dust clouds reflect light and give off heat, and so interfere with the search for planets. By helping to characterize these emissions to very deep limits, the LBTI will provide critically needed data for the design of future missions that will study and characterize planets orbiting nearby stars. The telescope is expected to be fully operational in 2009.

fireballs

name given to very bright meteors or bolides. It is formally defined as a meteor that would have a magnitude of -3 or brighter if seen at zenith.

McDonald Observatory

observatory in Texas that is the site of the Hobby-Eberly Telescope, a 9.2 meter (30 feet) aperture reflecting telescope.

Gregory, Frederick

the first African-American to pilot a spacecraft (1985, the Space Shuttle Challenger), and in 1989 he became the first African-American to command a space mission (the Space Shuttle Discovery)

Shepard, Alan

the first American in space, aboard the spacecraft Freedom 7 (the Mercury Redstone 3 mission). The suborbital flight lasted 15 minutes 28 seconds. Shepard also famously played golf on the Moon during the Apollo 14 mission.

Leavitt, Henrietta

the first to propose that Cepheid variables could be used to measure the distance to distant stars and galaxies. Leavitt began work in 1893 at Harvard College Observatory as one of the women human "computers" brought in by Edward Charles Pickering to measure and catalog the brightness of stars in the observatory's photographic plate collection. She noted thousands of variable stars in images of the Magellanic Clouds. In 1908 she published her results, noting that a few of the variables showed a pattern: brighter ones appeared to have longer periods. After further study, she confirmed in 1912 that the variable stars of greater intrinsic luminosity - actually Cepheid variables - did indeed have longer periods, and the relationship was quite close and predictable. Leavitt's discovery is known as 'Period-luminosity relationship.

omega

the ratio of the average density of the universe to the critical density of the universe. Einstein showed that gravity curves three-dimensional space, and that space in turn moves matter. For the universe as a whole, the shape of the curvature depends on the average density of the matter. If the average density of matter in the universe is greater than the critical density, the force of gravity will eventually rein in expansion and cause the universe to collapse upon itself. In this case, the universe is said to be positively curved, and omega, the ratio of the average density to the critical density, is greater than 1. Conversely, if the average density of matter in the universe is less than the critical density, gravity will lose its grip on matter and the universe will expand forever. This negatively curved universe is defined by an omega less than one. If omega is exactly one--that is, if the average density of the universe is equal to the critical density--then the universe will expand to a maximum density and remain there for eternity. This universe is flat; it has zero curvature. Current measurements show omega is approximately 0.3. As it turns out, omega has been inferred to be equal to one, and the lower values, it is thought, only represent an inability in the methods used to uncover all the dark matter that exists. So the universe remains open and flat and there is no future time at which all the galaxies will collapse into a future Big Bang.

libration

the slight rocking over time in both the north-south direction and the east-west direction experienced by the moon. Due to this rocking, about 59% of the moon's surface is visible from Earth over time (although only 50% is visible at any one time). The east-west wobble is a product of the moon's elliptical orbit. Maximum librations are seen about one week AFTER perigee and one week AFTER apogee, revealing (depending upon the month) up to 8 degrees of longitude on the Moon's far side. The north-south nodding results primarily from the approximate 5 degree tilt of the moon's orbital plane with respect to the ecliptic (the Earth's orbital plane). Add to that, the approximate 1.5 degree tilt of the Moon's equator to the ecliptic, and you have the inclination of the Moon's equator to the plane of its orbit around Earth at some 6.5 degrees (5 + 1.5 = 6.5). Consequently, during the month, you can see a maximum of 6.5 degrees of latitude beyond the Moon's north pole, and a fortnight later, 6.5 degrees past the south pole.

Grissom, Gus -Mercury-Redstone 4

the spacecraft Liberty Bell 7 (part of the Mercury-Redstone 4 mission) carried Gus Grissom on the second U.S. suborbital flight. The capsule sank in the ocean before recovery when the hatch unexpectedly blew off. Astronauts Gus Grissom, Edward White, and Roger Chaffee were killed when a fire erupted in their Apollo 1 spacecraft during a test on the launch pad. The spacecraft never launched.

CINDI (Coupled Ion Neutral Dynamic Investigation)

- CINDI hunts giant, radio-busting plasma bubbles. NASA's CINDI instrument is installed on the Air Force C/NOFS satellite. They come out at night over the equator -- giant bubbles of plasma, a gas of electrically charged particles, silently rise in the upper atmosphere. While invisible to human eyes, they can disrupt crucial radio communication and navigation signals, like the Global Positioning System (GPS). Plasma bubbles form at night because the thermosphere and ionosphere have a mix of plasma and electrically neutral gas which becomes unstable after sunset. During the daytime, radiation from the sun creates plasma by tearing electrons from atoms and molecules in the thermosphere and ionosphere. The solar radiation maintains relatively constant levels of plasma in these regions, so they are quite smooth and well behaved. But during the nighttime, there is no solar radiation to prevent the charged particles from recombining back into electrically neutral atoms or molecules again. The recombination happens faster at lower altitudes, because there are more heavy charged particles (molecular ions) there, and they recombine more quickly than charged particles made from single atoms. More rapid recombination makes the plasma less dense at lower altitudes. The region then becomes unstable because the less dense plasma below, which is trapped in the neutral gas, wants to rise above the higher density plasma above it. This nighttime instability actually happens at all latitudes, but the equatorial regions become especially turbulent because the plasma bubbles are suspended on Earth's magnetic field, which is horizontal over the equator.

Ares

- NASA's next-generation crew launch vehicle, the Ares I rocket. NASA's Ares rockets, named for the Greek god associated with Mars, will return humans to the moon and later take them to Mars and other destinations. Ares I, which uses a single five-segment solid rocket booster, a derivative of the space shuttle's solid rocket booster, for the first stage. A liquid oxygen/liquid hydrogen J-2X engine derived from the J-2 engine used on Apollo's second stage will power the crew exploration vehicle's second stage. The Ares I can lift more than 55,000 pounds to low Earth orbit. Planning and early design are under way for hardware, propulsion systems and associated technologies for NASA's Ares V cargo launch vehicle -- the "heavy lifter" of America's next-generation space fleet. Ares V will serve as NASA's primary vessel for safe, reliable delivery of large-scale hardware to space -- from the lunar landing craft and materials for establishing a moon base, to food, fresh water and other staples needed to extend a human presence beyond Earth orbit.

zodiacal light

- a faint, roughly triangular, whitish glow seen in the night sky which appears to extend up from the vicinity of the sun along the ecliptic. It is produced by sunlight reflecting off dust particles in the solar system known as cosmic dust. This material is known as the interplanetary dust cloud.

Aquarius

- a focused satellite mission to measure global Sea Surface Salinity (SSS). Scientific progress is limited because conventional in situ SSS sampling is too sparse to give the global view of salinity variability that only a satellite can provide. Aquarius is planning to launch in 2010.

Palomar Observatory

- a privately owned observatory located in San Diego County, California, on Palomar Mountain. It is owned and operated by the California Institute of Technology (Caltech). The observatory currently consists of four main instruments: the 200 inch (5.08 m) Hale telescope, the 48 inch (1.22 m) Samuel Oschin telescope, the 18 inch (457 millimeter) Schmidt telescope, and a 60 inch (1.52 m) reflecting telescope. In addition, the Palomar Testbed Interferometer is located at this observatory. The 200-inch (5.1 m) Hale Telescope (f/3.3) was the world's largest effective telescope for 45 years (1948 - 1993). The American astronomer Edwin Powell Hubble was the first astronomer to use the telescope for observing.

Advanced Technology Large-Aperture Space Telescope (ATLAST)

- a proposed 8 to 16-meter (320 to 640-inch) optical space telescope that if approved, built, and launched, would be a true replacement and successor for the Hubble Space Telescope (HST); with the ability to observe and photograph astronomical objects in the optical, ultraviolet, and infrared wavelengths, but with substantially better resolution than the Hubble.

Navy Prototype Optical Interferometer (NPOI)

- an interferometer operated by the US Naval Observatory, the Naval Research Laboratory and The Lowell Observatory. The facility is located on Anderson Mesa about 15 miles southeast of Flagstaff, Arizona. To date it has produced the highest resolution optical images of any astronomical instrument (this is likely to change when the CHARA array and Magdalena Ridge Observatory Interferometer begin operations). The first astronomical object imaged by NPOI was Mizar.

Lowell, Percival

- discovered the canals on Mars spurring the belief that there may be life on the red planet.

VLT (Very Large Telescope)

- the Very Large Telescope (VLT) is a system of four separate optical telescopes (the Antu telescope, the Kueyen telescope, the Melipal telescope, and the Yepun telescope) organized in an array formation, built and operated by the European Southern Observatory (ESO) at the Paranal Observatory on Cerro Paranal, a 2,635 m high mountain in the Atacama desert in northern Chile. Each telescope has an 8.2 m aperture. The array is complemented by four movable Auxiliary Telescopes (ATs) of 1.8 m aperture. The VLT consists of an arrangement of four large (8.2 meter diameter) telescopes, and optical elements which can combine them into an astronomical interferometer (VLTI) which is used to resolve small objects. The interferometer also includes a set of four 1.8 meter diameter movable telescopes dedicated to interferometric observations. The 8.2 meter telescopes have been named after some astronomical objects in the local Mapuche language: Antu (The Sun), Kueyen (The Moon), Melipal (The Southern Cross), and Yepun (Venus). In its interferometric operating mode, the light from the telescopes is reflected off mirrors and directed through tunnels to a central beam combining laboratory. The VLTI is intended to achieve an effective angular resolution of 0.002 arcsecond at a wavelength of 2 µm.

Clementine

- the objective of the mission was to test sensors and spacecraft components under extended exposure to the space environment and to make scientific observations of the Moon and the near-Earth asteroid 1620 Geographos. The Geographos observations were not made due to a malfunction in the spacecraft. The Clementine Laser Image Detection And Ranging (LIDAR) experiment was designed to measure the distance from the spacecraft to a point on the surface of the Moon using laser altimetry. Altimetry data was collected from 60 N to 60 S latitude on the moon.

Chandra X-Ray Observatory

- the world's most powerful X-ray telescope. It has eight-times greater resolution and is able to detect sources more than 20-times fainter than any previous X-ray telescope. X-rays are produced in the cosmos when matter is heated to millions of degrees. Such temperatures occur where high magnetic fields, or extreme gravity, or explosive forces, hold sway. The Chandra X-ray Observatory, which was launched by Space Shuttle Columbia in 1999, can better define the hot, turbulent regions of space. This increased clarity can help scientists answer fundamental questions about the origin, evolution, and destiny of the universe.

Apollo - human spaceflight program undertaken by NASA during the years 1961

1975 with the goal of conducting manned moon landing missions. US President John F. Kennedy announced a goal of landing on the moon by the end of the decade in 1961, and it was accomplished on July 20, 1969 by the landing of astronauts Neil Armstrong and Buzz Aldrin, with Michael Collins orbiting above during the Apollo 11 mission. Five other Apollo missions also landed astronauts on the Moon (Apollos 12, 14, 15, 16, and 17), the last one in 1972. These six Apollo spaceflights are the only times humans have landed on another celestial body. Since 6 missions landed on the Moon, a total of 12 people have set foot on the moon. Apollo was the third human spaceflight program undertaken by NASA, the space agency of the United States. It used Apollo spacecraft and Saturn launch vehicles, which were later used for the Skylab program and the joint American-Soviet Apollo-Soyuz Test Project. These later programs are thus often considered to be part of the overall Apollo program.

Apollo 14

Alan Shepard famously played golf on the Moon during this mission.

Explorer 1

America's first satellite, which went into space in 1958. The satellite was a response to the Soviet launch of Sputnik 1 in 1957. It was developed under the direction of Dr. Wernher von Braun. The primary science instrument on Explorer 1 was a cosmic ray detector designed to measure the radiation environment in Earth orbit. Once in space this experiment, provided by Dr. James Van Allen of the University of Iowa, revealed a much lower cosmic ray count than expected. Van Allen theorized that the instrument may have been saturated by very strong radiation from a belt of charged particles trapped in space by Earth's magnetic field. The existence of these radiation belts was confirmed by another U.S. satellite launched two months later, and they became known as the Van Allen Belts in honor of their discoverer.

Stefan, Josef

Austrian physicist, born in Slovenia, who is best known for stating that the total radiation from a black body is proportional to the fourth power of its thermodynamic temperature. Stefan deduced the law from experimental measurements made by the Irish physicist John Tyndall. In 1884 the law was derived theoretically in the framework of thermodynamics by Stefan's student Ludwig Boltzmann and hence is known as the Stefan-Boltzmann law. Boltzmann treated a heat engine with light as a working matter. Today we derive the law from Planck's law of black body radiation and is valid only for ideal black objects. With his law Stefan determined the temperature of the Sun's surface and he calculated a value of 5430 °C. This was the first sensible value for the temperature of the Sun.

Huygens, Christiaan

Dutch scientist who proposed the wave theory of light. He developed the pendulum clock in 1657. He discovered polarization, and observed Saturn's rings. He discovered Titan in 1655.

Kuiper, Gerard

Dutch-American astronomer who postulated the presence of thousands of icy planetesimals in an extended region at the edge of the solar system beyond the orbit of Pluto now called the Kuiper Belt. Kuiper discovered two Uranus's satellite Miranda and Neptune's satellite Nereid. In addition, he discovered carbon dioxide in the atmosphere of Mars and the existence of a methane-laced atmosphere above Saturn's satellite Titan in 1944.

Flamsteed, John

English astronomer who was the first Astronomer Royal of England. Flamsteed numbers (designations) for stars are similar to Bayer designations, except that they use numbers instead of Greek letters. Each star is assigned a number and the Latin genitive of the constellation it lies in. Flamsteed designation contained 2554 stars. The numbers were originally assigned in order of increasing right ascension within each constellation, but due to the effects of precession they are now slightly out of order in some places. This method of designating stars first appeared in a preliminary version of John Flamsteed's Historia coelestis Britannica which was published by Edmond Halley and Isaac Newton in 1712 without Flamsteed's approval. Examples of well-known stars which are usually referred to by their Flamsteed numbers include 51 Pegasi and 61 Cygni.

Laplace, Pierre-Simon

French astronomer who put forth the nebular hypothesis for the origin of the Solar System. He also said that solar wind accounts for the slowed rotation of the sun and calculated how big the sun would have to be in order to become a black hole.

ROSAT (Röntgen Satellite)

German X-ray telescope that completed the first ever all-sky survey of x-rays in 1991.

Bode, Johann

German astronomer famous for developing Bode's Law (sometimes called the Titius-Bode law). This hypothesis states that bodies in some orbital systems, including the Sun's orbit at semi-major axes in an exponential function of planetary sequence. The hypothesis correctly predicted the orbits of Uranus and Ceres, but failed as a predictor of Neptune's orbit. He thought that a planet should be located where the asteroid belt is located, but the masses of all of the asteroids take the place of this predicted planet.

Encke, Johann

German astronomer who discovered a second gap in Saturn's rings from his Berlin observatory.

Fraunhofer, Joseph

German physicist and optician who discovered dark lines in the Sun's emission spectrum, called Fraunhofer lines. He used the lines as reference points for measuring the indices of refraction and the dispersive powers of various samples of glass. He also invented color-fringe-free (achromatic) lenses for telescopes. He also invented the diffraction grating and in doing so transformed spectroscopy from a qualitative art to a quantitative science by demonstrating how one could measure the wavelength of light accurately. He found out that the spectra of Sirius and other first-magnitude stars differed from each other and from the sun, thus founding stellar spectroscopy.

Paschen, Louis

German scientist who proved that the helium found on Earth is the same as that on the Sun. He is remembered by a series of lines in the hydrogen spectrum that were named after him.

Thales

Greek philosopher who was regarded by many, including Aristotle, as the first philosopher in the Greek tradition. Before Thales, the Greeks explained the origin and nature of the world through myths of anthropomorphic gods and heroes. Phenomena such as lightning or earthquakes were attributed to actions of the gods. In contrast to these mythological explanations, Thales attempted to find naturalistic explanations of the world, without reference to the supernatural. He explained earthquakes by hypothesizing that the Earth floats on water, and that earthquakes occur when the Earth is rocked by waves. He predicted a solar eclipse and believed that everything was compounded from water. With 5 fundamental propositions, he laid down the foundations on which classical geometry was raised. He also introduced the notion of proof by the deductive method.

Cassini - Cassini

Huygens is a joint NASA/ESA robotic spacecraft mission currently studying the planet Saturn and its moons. The spacecraft consists of two main elements: the NASA Cassini orbiter, named after the Italian-French astronomer Giovanni Domenico Cassini, and the ESA Huygens probe, named after the Dutch astronomer, mathematician and physicist Christiaan Huygens. It was launched in 1997 and entered into orbit around Saturn in 2004. In 2004 the Huygens probe separated from the orbiter; it reached Saturn's moon Titan in 2005 where it made an atmospheric descent to the surface and relayed scientific information. Cassini is the first spacecraft to orbit Saturn and the fourth to visit it. Cassini has discovered 4 new moons of Saturn. During the first two close flybys of the moon Enceladus in 2005, Cassini discovered a "deflection" in the local magnetic field that is characteristic for the existence of a thin but significant atmosphere. Other measurements obtained at that time point to ionized water vapor as being its main constituent. Cassini also observed water ice geysers erupting from the south pole of Enceladus, which gives more credibility to the idea that Enceladus is supplying the particles of Saturn's E ring. Mission scientists hypothesize that there may be pockets of liquid water near the surface of the moon that fuel the eruptions, making Enceladus one of the few bodies in our solar system to contain liquid water. Small, icy Enceladus is of great scientific interest because it is surprisingly active. Cassini discovered an icy plume shooting from this moon, and subsequent observations have revealed the spray contains complex organic chemicals. Tidal heating is keeping it warm, and hotspots associated with the fountains have been pinpointed. With heat, organic chemicals and potentially, liquid water, Enceladus could be a place where primitive lifeforms might evolve. In images captured in 2005, Cassini finally detected spokes in Saturn's rings. During the primary mission Cassini investigated the structure and complex organic chemistry of Titan's thick, smog-filled atmosphere. On the frigid, alien surface, the spacecraft and its Huygens probe revealed vast methane lakes and widespread stretches of wind-driven hydrocarbon sand dunes. Cassini researchers also deduced the presence of an internal, liquid water-ammonia ocean. Radar images obtained on July 21, 2006 appear to show lakes of liquid hydrocarbon (such as methane and ethane) in Titan's northern latitudes. This is the first discovery of currently-existing lakes anywhere besides Earth. The lakes range in size from about a kilometer to one which is one hundred kilometers across. In 2007, JPL announced that it found strong evidence of seas of methane and ethane in the northern hemisphere. At least one of these is larger than any of the Great Lakes in North America. In November 2006, scientists discovered a storm at the south pole of Saturn with a distinct eyewall. This is characteristic of a hurricane on Earth and had never been seen on another planet before. Unlike a hurricane, the storm appears to be stationary at the pole. The storm is 8,000 kilometers (5,000 mi) across, 70 kilometres (43 mi) high with winds blowing 560 kilometers per hour (350 mph). Now, the healthy spacecraft is working overtime on the Cassini Equinox Mission, seeking answer to new questions raised in Cassini's first years at Saturn.

Cassini, Giovanni

Italian astronomer who discovered four moons of Saturn and the gap in the rings of Saturn now called the Cassini division. Between 1664-47 he determined the rotation periods of Mars, Jupiter and Venus. He distinguished two zones within what was thought to be a single ring around Saturn and suggested that they were composed of many tiny satellites.

New Horizons

NASA mission to Pluto, its moon Charon, and the Kuiper Belt. It launched in 2006 and is expected to reach Pluto in 2015. On the way in, the spacecraft will look for ultraviolet emissions from Pluto's atmosphere and make the best global maps of Pluto and Charon in green, blue, red and a special wavelength that is sensitive to methane frost on the surface. It will also take spectral maps in the near infrared, telling the science team about Pluto's and Charon's surface compositions and locations and temperatures of these materials. During the half-hour when the spacecraft is closest to Pluto or its largest moon, it will take close-up pictures in both visible and near-infrared wavelengths. The best pictures of Pluto will depict surface features as small as 200 feet (about 60 meters) across. After passing Pluto and Charon, pending NASA approval of an extended mission, the spacecraft can retarget itself for an encounter with a KBO (Kuiper Belt Object). The KBO target would not be selected until later in the mission, but scientists expect to find one or more the spacecraft can reach that are 30-60 miles (about 50-100 kilometers) across. This encounter would be similar to the Pluto-Charon encounter; the spacecraft would map the KBO, get its composition from infrared spectroscopy and four-color maps, and look for an atmosphere and moons.

Leonov, Alexy

Russian cosmonaut who became the first person to "walk in space", aboard the Voskhod 2 spacecraft - a Soviet manned space mission in March 1965.

RATAN-600

Russian radio telescope which consists of a 576 m diameter circle of rectangular radio reflectors, is also based at the observatory at an altitude of 970 m. Each of the 895 2×7.4 m reflectors can be pointed towards a central conical receiver or to one of five cylindric reflectors. Each reflector is combined with instrumentation cabin. The overall effect is that of a partially steerable antenna with the resolving power of a 600 m diameter dish (when using the central conical receiver), making it the world's largest diameter individual radio telescope.

Gagarin, Yuri

Soviet cosmonaut who was the first man in space, aboard the Vostok-1 spacecraft. Launch and landing occurred on April 12, 1961, with a total duration of 1 hour 48 minutes.

Tereshkova, Valentina

Soviet cosmonaut who was the first woman in space, aboard the Vostok-6 spacecraft. Launch occurred on June 16, 1963, and the mission lasted 3 days. This was the last mission of the Vostok program.

Venera 9

Soviet craft that in 1975 sent back the first images (black and white) of the surface of Venus.

Voskhod program

Soviet manned spaceflight program that was the successor to the Vostok program and predecessor to the Soyuz program. The two missions flown used the Voskhod spacecraft and rocket. The word 'Voskhod' means 'ascent' or 'dawn'. The Voskhod spacecraft was basically a Vostok spacecraft that had a backup, solid fuel retrorocket added to the top of the descent module.

Vostok-6

Soviet mission that carried the first woman into space, cosmonaut Valentina Tereshkova. Launch occurred on June 16, 1963, and the mission lasted 3 days. This was the last mission of the Vostok program.

Voskhod 1

Soviet mission that was the first spaceflight to carry more than one person into space, the first flight without space suits, the first to carry a scientist and a physician into space, and also set an altitude record of 336 km (209 mi). The craft was launched on October 12, 1964. This Soviet mission was specifically planned to beat the U.S. Gemini program to this milestone.

SERVIR

Spanish for "to serve," SERVIR is a Regional Visualization and Monitoring System that integrates earth observations (e.g. satellite imagery) and forecast models together with in situ data and knowledge for timely decision-making to benefit society. This program allows timely response to natural disasters in Mesoamerica (Central America) and Africa.

Viking 1 and 2

The Viking Mars mission was performed by two spacecraft, Viking 1 and Viking 2, launched within a couple of weeks of each other in 1975. Each spacecraft consisted of an orbiter and a lander, which traveled attached together for nearly a year to reach Mars orbit. The orbiters then began taking pictures of the Martian surface, from which a landing site was selected. The landers then separated from the orbiters and soft landed. The orbiters continued imaging and, between Viking 1 and Viking 2, imaged the entire planet at what was then high resolution. The orbiters also conducted atmospheric water vapor measurements and infrared thermal mapping. The Viking 1 orbiter flew within 90 kilometers of Phobos to take images of this larger, inner moon of Mars. The Viking landers took full 360-degree pictures, collected and analyzed samples of the Martian soil, and monitored the temperature, wind direction, and wind speed. The Viking missions revealed further details of volcanoes, lava plains, huge canyons, and the effects of wind and water. Analysis of the soils at the landing sites showed them to be rich in iron, but devoid of any signs of life.The results from the Viking experiments revolutionized our view of Mars. Volcanoes, lava plains, immense canyons, cratered areas, wind-formed features, and evidence of surface water were seen in the Orbiter images. The planet was found to be divided into two main regions, northern low plains and southern cratered highlands. Superimposed on these regions are the Tharsis and Elysium bulges, which are high-standing volcanic areas, and Valles Marineris, a system of giant canyons near the equator. The surface material at both landing sites was found to be an iron-rich clay. Measured temperatures ranged from 150 to 250 K, with a variation over a given day of 35 to 50 K. Seasonal dust storms, pressure changes, and transport of atmospheric gases between the polar caps were observed.

Magellan

a space probe sent to the planet Venus. Magellan was the first planetary spacecraft to be launched by a Space Shuttle (1989). Magellan created the first (and currently the best) near-photographic quality, high resolution mapping of the planet's surface features (using radar). Prior Venus missions had created low resolution radar globes of general, continent-sized formations. Magellan, however, finally allowed detailed imaging and analysis of craters, hills, ridges, and other geologic formations, to a degree comparable to the visible-light photographic mapping of other planets. Magellan's global radar map will remain the most detailed Venus map in existence for the foreseeable future, although the planned Russian Venera-D may carry a radar that can achieve the same, if not better resolution as the radar used by Magellan. Magellan was the first unmanned spacecraft to be launched by NASA since its successful Voyager 1 spacecraft to Jupiter and Saturn in 1977.

conjunction

alignment of two celestial bodies as seen from Earth. The two bodies occupy the right ascension (equivalent to longitude).

transit

an event in which one celestial body appears to move across the face of another celestial body, hiding a small part of it. For example, a transit of Venus across the Sun occurred in 2012. If the body passing in front of another body obscures all of the second body the event is called an occultation (stellar occultation if a star is obscured).

LBTI (Large Binocular Telescope Interferometer)

an instrument that is part of the LBT (Large Binocular Telescope) in Arizona. The LBTI employs nulling and Fizeau interferometry. Nulling interferometry is a technique that cancels the overwhelming glare from a star by interference of light. This allows the detection of nearby planets or dust disks which would otherwise be obscured by the much brighter star. The instrument is comprised of a central beam combiner that directs the optical beam from each primary mirror into the Nulling Imaging Camera. All the optics are cooled to 100 Kelvin or below to reduce thermal emissions.

Fermi Gamma-Ray Space Telescope (formerly called GLAST)

an international and multi-agency space observatory launched in 2008 that will study the cosmos in the photon energy range of 8,000 electronvolts (8 keV) to greater than 300 billion electronvolts (300 GeV). An electronvolt is a unit of energy close to that of visible light, so Fermi will catch photons with energies thousands to hundreds of billions of times greater than those we see with our eyes. Fermi carries two instruments: the Large Area Telescope (LAT) and the GLAST Burst Monitor (GBM). The LAT has four subsystems that work together to detect gamma rays and to reject signals from the intense bombardment of cosmic rays. For every gamma ray that enters the LAT, it will have to filter out 100,000 to one million cosmic rays, charged particles that resemble the particles produced by gamma rays. The GBM consists of 12 detectors made of sodium iodide for catching X rays and low-energy gamma rays, and two detectors made of bismuth germanate for high-energy gamma rays. Together, they detect cover X rays and gamma rays in the energy range between 8 keV to 30 MeV, overlapping with the LAT's lower-energy limit. The GBM detectors will view the entire sky not occulted by Earth, and are expected to pick up about 200 GRBs per year, as well as solar flares and other transient events. The combination of the GBM and the LAT provides a powerful tool for studying GRBs over a very wide range of energies. Fermi data will enable scientists to answer persistent questions across a broad range of topics, including supermassive black-hole systems, pulsars, the origin of cosmic rays, and searches for signals of new physics.

Pythagoras

ancient Greek that was the first to teach that the Earth was spherical in shape.

Hipparchus

ancient Greek who was the first man to classify stars according to their brightness. Discovered precession and made the first catalog of stellar magnitudes. He calculated the year to be 365 days and 5 Hours with seasons of varying length. He calculated the length of a month to within one second in 150 B.C.

Tombaugh, Clyde

astronomer who is best known for discovering the dwarf planet Pluto in 1930, but also discovered many asteroids, and called for serious scientific research of unidentified flying objects. While a young researcher working for the Lowell Observatory in Flagstaff, Arizona, Tombaugh was given the job to perform a systematic search for a trans-Neptunian planet (also called Planet X), which had been predicted by Percival Lowell and William Pickering. Tombaugh used the observatory's 13-inch astrograph to take photographs of the same section of sky several nights apart. He then used a blink comparator to compare the different images. When he shifted between the two images, a moving object, such as a planet, would appear to jump from one position to another, while the more distant objects such as stars would appear stationary. Tombaugh noticed such a moving object in his search, and subsequent observations showed it to be the object we call Pluto.

Baily's beads

beads of sunlight visible around the Moon during a total solar eclipse. As the moon "grazes" by the Sun during a solar eclipse, the rugged lunar limb topography allows beads of sunlight to shine through in some places, and not in others. This effect is called Baily's beads, in honor of Francis Baily, who first provided an exact explanation of the phenomenon in 1836. Lunar topography has considerable relief because of the presence of mountains, craters, valleys, etc. While Baily's beads are seen briefly for a few seconds at the center of the eclipse path, their duration is maximized near the edges of the path of the umbra, reaching 1-2 minutes.

Babcock, Harold

developed the solar magnetograph, which allowed him and other scientists to make detailed investigations of the Sun's magnetic fields.

Bond, George and William

discovered Hyperion, a moon of Saturn.

Bell, Jocelyn

discovered neutron stars.

Apollo 17

final Apollo lunar mission (1972), and only night launch.

Apollo 9

first manned flight of the Lunar Module, the craft that would later be used to land on the moon.

Apollo-Soyuz Test Project

last mission of the Apollo program and the first joint flight of the U.S. and Soviet space programs. The mission entailed the docking of the American Apollo spacecraft (referred to by some as Apollo 18) with the Soviet Soyuz 19 spacecraft. Astronauts Stafford and Leonov exchanged the first international handshake in space through the open hatch of the Soyuz. The two spacecraft remained linked for 44 hours, long enough for the three Americans and two Soviets to exchange flags and gifts (including tree seeds which were later planted in the two countries), sign certificates, pay visits to each other's ships, eat together and converse in each other's languages. (Because of Stafford's pronounced drawl when speaking Russian, Leonov later joked that there were actually three languages spoken on the mission: Russian, English, and "Oklahomski."). After forty-four hours together, the two ships separated, and maneuvered to use the Apollo to create an artificial solar eclipse to allow the crew of the Soyuz to take photographs of the solar corona.

Lunar Prospector

launched in 1998, it was successfully placed into orbit 63 miles above the lunar surface five days later. The studies conducted by the spacecraft and its five instruments were designed to provide insights into lunar origin and evolution and determine whether or not water ice is present in the Moon's polar regions. Besides water, Lunar Prospector searched for other natural resources, such as minerals and gases, that could be used to build and sustain a future human lunar base or to manufacture fuel for launching spacecraft from the Moon to the rest of the Solar System. The science data returned from Lunar Prospector has enabled scientists to create the most complete and detailed maps of the gravity, magnetic properties and chemical composition of the Moon's entire surface. While the Moon's magnetic field is relatively weak, Prospector detected large localized magnetic fields that create the two smallest magnetospheres in the Solar System. The craft was crashed into a crater in attempt to kick up water ice - none was detected, though.

SORCE (Solar Radiation and Climate Experiment)

launched in 2003, this satellite provides state-of-the-art measurements of incoming x-ray, ultraviolet, visible, near-infrared, and total solar radiation. SORCE represents the merging of the EOS Solar Stellar Irradiance Comparison Experiment (SOLSTICE) and the Total Solar Irradiance Mission (TSIM). The measurements provided by SORCE specifically address long-term climate change, natural variability and enhanced climate prediction, and atmospheric ozone and UV-B radiation. SORCE measures the Sun's output with the use of state-of-the-art radiometers, spectrometers, photodiodes, detectors, and bolometers engineered into instruments mounted on a satellite observatory. These measurements are critical to studies of the Sun, its effect on our Earth system, and its influence on humankind.

STEREO (Solar Terrestrial Relations Observatory)

launched in 2006, this mission provides a unique and revolutionary view of the Sun-Earth System. The two nearly identical observatories - one ahead of Earth in its orbit, the other trailing behind - trace the flow of energy and matter from the Sun to Earth as well as reveal the 3D structure of coronal mass ejections and help us understand why they happen. STEREO also provides alerts for Earth-directed solar ejections, from its unique side-viewing perspective adding it to the fleet of Space Weather detection satellites. Coronal mass ejections (CMEs), are powerful eruptions that can blow up to 10 billion tons of the Sun's atmosphere into interplanetary space. Traveling away from the Sun at speeds of approximately one million mph (1.6 million kph), CMEs can create major disturbances in the interplanetary medium and trigger severe magnetic storms when they collide with Earth's magnetosphere.

Dawn

launched in 2009, this spacecraft is traveling to the two oldest and most massive asteroids in our solar system, Vesta and Ceres. By observing both minor planets with the same set of instruments, Dawn will provide new answers to questions about the formation and evolution of the early solar system. It is the first Discovery mission to be powered by ion propulsion, an advanced technology successfully demonstrated by NASA's Deep Space 1 mission. The use of solar electric ion thrusters will enable Dawn to carry enough fuel and adjust its velocity to orbit and study two asteroids in one mission, a feat that has not been attempted before. Dawn orbited Vesta from 2011 to 2013 and is now headed toward Ceres. These minor planets have remained intact since the earliest time of solar system formation. Their surfaces are believed to contain a snapshot of the conditions present in the solar system's first 10 million years, allowing Dawn to investigate both the origin of the solar system and its present state.

Shenzhou 7

mission in 2008 that carried out the first Chinese spacewalk, by Zhai Zhigang.

Kepler

mission launched in 2009. The scientific goal of the Kepler Mission is to explore the structure and diversity of planetary systems, with a special emphasis on the detection of Earth-size planets. It will survey the extended solar neighborhood to detect and characterize hundreds of terrestrial and larger planets in or near the "habitable zone," defined by scientists as the distance from a star where liquid water can exist on a planet's surface. Kepler will monitor 100,000 stars similar to our sun for four years. The results will be extremely important either way. If Kepler detects many habitable, Earth-size planets, it could mean the universe is full of life. Kepler would then be a stepping stone to the next extensive search for habitable planets and life, the Terrestrial Planet Finder. When a planet passes in front of a star as viewed from Earth, the event is called a "transit". On Earth, we can observe an occasional Venus or Mercury transit. These events are seen as a small black dot creeping across the Sun—Venus or Mercury blocks sunlight as the planet moves between the Sun and us. Kepler finds planets by looking for tiny dips in the brightness of a star when a planet crosses in front of it—we say the planet transits the star. Once detected, the planet's orbital size can be calculated from the period (how long it takes the planet to orbit once around the star) and the mass of the star using Kepler's Third Law of planetary motion. The size of the planet is found from the depth of the transit (how much the brightness of the star drops) and the size of the star. From the orbital size and the temperature of the star, the planet's characteristic temperature can be calculated. From this the question of whether or not the planet is habitable (not necessarily inhabited) can be answered. Since transits only last a fraction of a day, all the stars must be monitored continuously, that is, their brightnesses must be measured at least once every few hours. The ability to continuously view the stars being monitored dictates that the field of view (FOV) must never be blocked at any time during the year. Therefore, to avoid the Sun the FOV must be out of the ecliptic plane. The secondary requirement is that the FOV have the largest possible number of stars. This leads to the selection of a region in the Cygnus and Lyra constellations of our Galaxy. Two of the telescope's gyroscope-like reaction wheels, which are used to precisely point the spacecraft, failed in 2012 and 2013, apparently ending its mission. In 2014, a team of scientists crafted a resourceful strategy to use pressure from sunlight by pointing the telescope in the plane of Earth's orbit, the ecliptic, as a "virtual reaction wheel" to help control and stabilize the spacecraft, and its new K2 mission is now collecting data. Kepler-78b was the first exoplanet discovered to have both a measured mass and size near that of Earth's, indicating it is made primarily of rock and iron. Kepler-10b was the first rocky planet discovered, 1.4 times the size of Earth. Kepler-186f was the first Earth-sized planet discovered to be orbiting its star in the habitable zone. A new method of finding exoplanets that relies on Einstein's special theory of relativity is called relativistic BEaming, Ellipsoidal, and Reflection/emission modulations (BEER). The new method looks for three small effects that occur simultaneously as a planet orbits the star. Einstein's "beaming" effect causes the star to brighten as it moves toward us, tugged by the planet, and dim as it moves away. The brightening results from photons "piling up" as energy, as well as light getting focused in the direction of the star's motion due to relativistic effects. Another recently used technique is called verification by multiplicity, which relies in part on the logic of probability. This method can be likened to the behavior we know of lions and lionesses. In our imaginary savannah, the lions are the Kepler stars and the lionesses are the planet candidates. The lionesses would sometimes be observed grouped together whereas lions tend to roam on their own. If you see two lions it could be a lion and a lioness or it could be two lions. But if more than two large felines are gathered, then it is very likely to be a lion and his pride. Thus, through multiplicity the lioness can be reliably identified in much the same way multiple planet candidates can be found around the same star. As of early 2015, Kepler has discovered 1000 verified exoplanets, 8 of which are less than twice Earth-size and in their star's habitable zone (all 8 orbit stars cooler and smaller than our Sun). The IAU definition for exoplanets includes only objects with a mass below the limiting mass for thermonuclear fusion of deuterium, which is currently calculated to be 13 Jupiter masses for objects of solar metallicity. Substellar objects with masses above this mass are considered brown dwarfs. Free-floating objects in young star clusters with masses below the limiting mass for thermonuclear fusion of deuterium are not "planets", but are "sub-brown dwarfs". The firs exoplanets discovered were dubbed "hot Jupiters", and were sizzling gas giants with rapid orbits circling close to their host stars. Hot Jupiter more often circle stars with high metallicity (elements heavier than hydrogen and helium). Other categories include those smaller than 1.7 times the size of Earth, around stars whose metallicity is roughly solar. These are the terrestrial planets we are familiar with. At a slightly higher metallicity, stars are more likely to have planets between 1.7 and 3.9 times the size of Earth — dubbed gas dwarfs by the team — that have rocky cores and thick atmospheres of hydrogen and helium, of which there are no solar system equivalents.Above 3.9 times the size of Earth are familiar gas and ice giants, which are more common around stars with an even higher metallicity (about 1.5 times solar), in agreement with previous studies. The results suggest that there's a metallicity sweet spot for terrestrial planets to form, roughly the same as the Sun's. That bodes well for forming Earth-like planets around Sun-like stars.

Mars Reconnaissance Orbiter

mission on a search for evidence that water persisted on the surface of Mars for a long period of time. While other Mars missions have shown that water flowed across the surface in Mars' history, it remains a mystery whether water was ever around long enough to provide a habitat for life. instruments zoom in for extreme close-up photography of the martian surface, analyze minerals, look for subsurface water, trace how much dust and water are distributed in the atmosphere, and monitor daily global weather.These studies are identifying deposits of minerals that may have formed in water over long periods of time, looking for evidence of shorelines of ancient seas and lakes, and analyzing deposits placed in layers over time by flowing water. The mission is examining whether underground martian ice discovered by the Mars Odyssey orbiter is the top layer of a deep ice deposit or a shallow layer in equilibrium with the atmosphere and its seasonal cycle of water vapor. Its imaging spectrometer looks at small-scale areas about five times smaller than a football field, a scale perfect for identifying any hot springs or other small water features. One of the mission's main goals is to map the Martian landscape with its high-resolution cameras in order to choose landing sites for future surface missions. The MRO played an important role in choosing the landing site of the Phoenix Lander, which is now exploring the Martian Arctic in Green Valley. In addition, MRO is looking for the remains of the previously lost Mars Polar Lander and Beagle 2 spacecraft, and serves as the first step in setting up an internet protocol network for the planets in our solar system.[citation needed] After its main science operations are completed, the probe's extended mission is to be the communication and navigation system for landers and rover probes. The mission is set to end in 2010.

Gemini 4

mission that included the first American spacewalk. The spacewalk was 23 minutes long and performed by Edward White in 1965.

Hinode (Solar-B)

mission to investigate the interaction between the Sun's magnetic field and the corona. The goals of the mission are: 1) to understand how energy generated by magnetic-field changes in the lower solar atmosphere (photosphere) is transmitted to the upper solar atmosphere (corona), 2) to understand how that energy influences the dynamics and structure of that upper atmosphere, and 3) to determine how the energy transfer and atmospheric dynamics affects the interplanetary-space environment.

Genesis

mission which sent a spacecraft to collect particles of the solar wind. The mission was designed to answer 2 questions: What is the sun made of, and are the Earth and planets made of the same materials? It was launched in 2001, and crash landed in the Utah desert in 2004, after its drogue parachute and parafoil failed to deploy. Three of the four segments of the sample concentrator remained intact after the crash. Designed to measure the isotopic ratios of oxygen and nitrogen, these segments contain the mission's most important science goal. The fourth was broken but all the pieces were there. They also discovered the gold foil collector, the number two priority for science recovery, was undamaged and in excellent condition. The gold foil is expected to contain almost a million billion atoms of solar wind.

star visibility

on a clear, dark, moonless night on Earth, approximately 3,000 stars are visible to the naked eye.

Aura

satellite that studies ozone, air quality, composition, chemistry, and dynamics of the Earth's atmosphere. It also studies air quality and climate. It was launched in 2004, and is set to operate until 2009 or 2010.

NOAA-N Prime (renamed NOAA-19)

satellite that will improve weather forecasting and monitor environmental events around the world. NOAA-N Prime is the fifth and last in the current series of five polar-orbiting satellites with improved imaging and sounding capabilities. The satellite will collect meteorological data and transmit the information to NOAA's Satellite and Information Service, which processes the data for input to the National Weather Service for its long-range weather and climate forecasts. Forecasters worldwide also will be able to access the satellite's images and data. NOAA-N Prime has sensors that will be used in the Search and Rescue Satellite-Aided Tracking System to monitor for distress signals around the world. NOAA-N Prime replaced NOAA-18 in a 2:00 p.m. local solar time orbit as the primary afternoon spacecraft. NOAA-N Prime will carry the same primary instruments as NOAA-18 plus an Advanced Data Collection System and an improved Search and Rescue Processor provided by France. The satellite carries an Advanced Very High Resolution Radiometer (AVHRR), which takes very high resolution photographs.

Juno

scheduled for launch in 2011, the primary scientific goal of the Juno mission is to significantly improve our understanding of the formation, evolution and structure of Jupiter. In 2016, the spinning, solar-powered Juno spacecraft will reach Jupiter and enter into a highly elliptical polar orbit that skims only 5000 kilometers above the planet's atmosphere. Jupiter has no solid surface. Instead its hydrogen and helium dominated atmosphere grows steadily denser with depth. Ultimately, but we don't know exactly where, the atmosphere must become a fluid in which hydrogen acts like an electrically conducting metal. Still deeper there may be a core of heavy elements and somewhere, somehow, an intense magnetic field is generated. The invisible external tendrils of that field guide charged particles that crash into the polar ionospheres, producing the most intense auroras (the northern and southern "lights") in the solar system. Juno will study these and other characteristics that make Jupiter one of the most fascinating planets in the solar system. To answer our fundamental questions about origins we especially need to know Jupiter's internal structure and global water abundance. Juno will map the internal structure by studying its influence on the planet's gravitational field with unprecedented accuracy. Juno also will carry a color camera to give the public a first look at Jupiter's poles.

Aldrin, Buzz

second person to set foot on the Moon, after Neil Armstrong, on July 20, 1969, as part of the Apollo 11 mission.

Contour (Comet Nucleus Tour)

space probe launched in 2002 that failed shortly after launch. Its mission was to visit the nuclei of the comets Encke and Schwassmann-Wachmann-3. At each comet flyby, the spacecraft was to get as close as 60 miles to the comet nucleus to capture high resolution pictures, perform detailed compositional analyses of gas and dust, and determine the comet's precise orbit. This information would have dramatically improved our knowledge of comet nuclei and their diversity.

NEAR (Near-Earth Asteroid Rendezvous)

spacecraft that studied the asteroid Eros. It launched in 1996 and made the first landing on an asteroid when it touched down on Eros in 2001. Eros is the largest of the so-called near-Earth asteroids whose orbits cross that of Earth's. These bodies are of interest because of their potential for collision with Earth, as well as for the clues they hold about the nature of how small bodies, including the Earth, were formed. The mission allowed the formation of the first detailed map and three-dimensional model of an asteroid. Previously scientists had theorized that asteroids were either solid iron or cosmic rubble piles-Eros is neither. Data suggests that Eros is a cracked but solid rock, possibly a fractured chip off a larger body, made of some of the most primitive materials in the solar system.

Zanstra temperature

temperature of a star that can be estimated by the amounts of emission of ionized helium and hydrogen from the nebula surrounding the star. The amount of ionized-helium radiation is determined by the number of photons of more than 54 volts energy, while hydrogen is ionized by photons in excess of 13.6 volts. The relative numbers of photons in the two groups depends strongly on temperature, since the spectrum shifts dramatically to higher energies as the temperature of the star increases. Hence, the temperature can be found from the observed strengths of the hydrogen and helium lines.

Lawrence, Robert

the first African-American astronaut (1967), but he never made it into space.

galactic year

the length of time it takes our Sun to orbit the galaxy - about 225 million years.

Mercury-Atlas 6

the spacecraft Friendship 7 made John Glenn the first American to orbit the Earth. The 3 orbits lasted 4 hours 55 minutes.

Mercury-Redstone 4

the spacecraft Liberty Bell 7 carried Gus Grissom on the second U.S. suborbital flight. The capsule sank in the ocean before recovery when the hatch unexpectedly blew off.

sun dogs

two bright spots of light on opposite sides of a halo around the Sun. The effect arises from the refraction of light through hexagonal ice crystals and is common in cirrostratus (where they occur in pairs, one on each side of the Sun) and cirrus clouds. Sun dog is a popular term, of obscure origin, for a parhelion, or mock sun.

Apollo 2, 3, 4, 5, and 6

unmanned missions that tested fuel tanks, the command module, and the Saturn IB and Saturn V booster rockets.

WISE (Widefield Infrared Survey Explorer)

with a launch scheduled for 2009, WISE is an unmanned satellite carrying an infrared-sensitive telescope that will image the entire sky. Since objects around room temperature emit infrared radiation, the WISE telescope and detectors are kept very cold (below -430º F / 15º K, which is only 15º Centigrade above absolute zero) by a cryostat - like an ice chest but filled with solid hydrogen instead of ice. As WISE sweeps along the circle, a small mirror scans in the opposite direction, capturing an image of the sky every 11 seconds. Each picture will cover an area of the sky 3 times larger than the full Moon. After 6 months, WISE will have taken nearly 1,500,000 pictures covering the entire sky. Each picture will have one megapixel resolution at each of the four different wavelengths that range from 5 to 35 times longer than the longest waves the human eye can see. WISE will provide an all-sky survey from 3 to 25 μm with 500,000 times the sensitivity of COBE/DIRBE and 500 times that of IRAS. The survey will help search for the origins of planets, stars, and galaxies and create an infrared atlas whose legacy will endure for decades.

IRAM 30-m

- a radio telescope for astronomical observations in the millimeter range of wavelengths, operated by the Institute for Radio Astronomy in the Millimeter Range (IRAM)) and located on the Sierra Nevada, in Spain, close to the Pico Veleta peak. It is the largest millimeter telescope in the world, but it will be surpassed when the ALMA is completed in 2012.

Vulcan

- a small planet proposed to exist in an orbit between Mercury and the Sun. There were some things about Mercury's orbit that astronomers couldn't explain, and in the 19th-century the French astronomer Le Verrier hypothesized that they were the result of another planet, which he named Vulcan. Although he was wrong, and Mercury's orbit has now been explained by Albert Einstein's theory of general relativity.

Lowell Observatory

- an astronomical observatory in Flagstaff, Arizona. Lowell Observatory is among the oldest observatories in the United States, and was designated a National Historic Landmark in 1965. It was founded in 1894 by astronomer Percival Lowell. The observatory operates several telescopes at two locations in Flagstaff. The main facility, located on Mars Hill just west of downtown Flagstaff, houses the original 24-inch (0.61 m) Clark Refracting Telescope, although its role today is as a public education tool and not research. The telescope, built in 1896 for $20,000, was assembled in Boston by Alvan Clark and then shipped by train to Flagstaff. Also located on the Mars Hill campus is the 13-inch (0.33 m) Pluto Discovery Telescope, used by Clyde Tombaugh in 1930 to discover the dwarf planet Pluto. Lowell Observatory is currently building the 4.2-meter Discovery Channel Telescope in partnership with Discovery Communications, Inc. Lowell is a partner with the United States Naval Observatory and NRL in the Navy Prototype Optical Interferometer (NPOI) located at its Anderson Mesa dark sky site.

Glenn, John

- the first American to orbit the Earth, aboard the spacecraft Friendship 7 (part of the Mercury-Atlas 6 mission). The 3 orbits lasted 4 hours 55 minutes.

Eddington, Arthur

English astronomer who established the law of the relationship of the mass of a star to its luminosity, and showed that the inward gravitational pressures in a star must be in exact balance with the outward forces caused by gas pressure and radiation. The Eddington limit, the natural limit to the luminosity of stars, or the radiation generated by accretion onto a compact object, is named in his honor. He is famous for his work regarding the theory of relativity. Eddington wrote a number of articles which announced and explained Einstein's theory of general relativity to the English-speaking world. He also conducted an eclipse expedition in 1919 that provided one of the earliest confirmations of relativity, and became known for his popular expositions and interpretations of the theory.

Schiaparelli, Giovanni

Italian astronomer whose contributions are his telescopic observations of Mars. In his initial observations, he named the "seas" and "continents" of Mars. He observed a dense network of linear structures on the surface of Mars which he called "canali" in Italian, meaning "channels" but mistranslated as "canals". While the latter term indicates an artificial construction, the former indicates the connotation that it can also be a natural configuration of the land. From this incorrect translation, various assumptions about life on Mars derived, as the "canals" of Mars soon became famous, giving rise to waves of hypotheses, speculation and folklore about the possibility of life on Mars. Among the most fervent supporters of the artificial canals was the famous American astronomer Percival Lowell who spent much of his life trying to prove the existence of intelligent life on the red planet. Later, however, with notable thanks to the observations of Italian astronomer Vicenzo Cerulli, scientists ascertained that the famous channels were actually mere optical illusions

Copernicus

Polish astronomer who believed that the Sun was in the center of the Solar System, and not the Earth. His flaw was that he believed the planets were in circular orbits. His work was an important precedent for later astronomers. He wrote the famous book On the Revolutions of the Heavenly Spheres.

Cooper, Leroy

first American in space for over a day aboard the spacecraft Faith 7 (part of the Mercury-Atlas 9 mission), which carried him on 22 orbits of the Earth.

White, Edward

first American to conduct a spacewalk. He died along with astronauts Grissom and Chafee in the Apollo 1 accident.

McAuliffe, Christa

she was scheduled to become the first teacher in space. She was planning to conduct experiments and teach two lessons from Space Shuttle Challenger. On January 28, 1986, her spacecraft disintegrated 73 seconds after launch and she was one of seven crew members killed in the Space Shuttle Challenger disaster.

opposition

the position of a body when it lies opposite the Sun in the sky as seen from Earth.

superior conjunction

the position of a planet when it passes behind the Sun, as seen from Earth.

inferior conjunction

the position of a planet when it passes between the Earth and the Sun.

cosmology

the study of the origin and evolution of the universe.

Apollo 18, 19, and 20

cancelled due to budget cuts.

Apollo 16

accomplished the first landing in the lunar highlands.

Sudbury Neutrino Observatory (SNO)

- a neutrino observatory located 6800 feet (about 2 km) underground in Vale Inco's Creighton Mine in Sudbury, Ontario, Canada. The detector was designed to detect solar neutrinos through their interactions with a large tank of heavy water. In 1984 Herb Chen of the University of California at Irvine first pointed out the advantages of using heavy water as a detector for solar neutrinos. Unlike previous detectors, using heavy water would make the detector sensitive to two reactions, one sensitive to all neutrino flavors, which would allow a detector to measure neutrino oscillations directly. The Creighton mine in Sudbury, among the deepest in the world and blessed with low background radiation, was quickly identified as an ideal place for Chen's proposed experiment to be built. The detector turned on in 1999, and was turned off in 2006. SNO was the first detector able to detect neutrino oscillation, solving the solar neutrino problem.While new data is no longer being taken the SNO collaboration will continue to analyze the data taken during that period for the next several years. The equipment is currently being refurbished for use in the SNO+ experiment.

VLA (Very Large Array)

- a radio astronomy observatory located fifty miles (80 km) west of Socorro, New Mexico, USA, at an altitude of 6970 ft (2124 m) above sea level. It is a component of the National Radio Astronomy Observatory (NRAO). The observatory consists of 27 independent antennas, each of which has a dish diameter of 25 meters (82 feet) and weighs 209 metric tonnes (230 Short tons). The antennas are arrayed along the three arms of a Y-shape (each of which measures 21 km/13 miles long). Using the railroad tracks that follow each of these arms and a specially designed lifting locomotive, the antennas can be physically relocated to a number of prepared positions, allowing aperture synthesis interferometry with a maximum baseline of 36 km (22.3 miles): in essence, the array acts as a single antenna with that diameter. The smallest angular resolution that can be reached is about 0.05 arcseconds at a wavelength of 7 mm. There are four commonly used configurations, designated A (the largest) through D (the tightest, when all the dishes are within 600 m of the center point). The observatory normally cycles through all the various possible configurations (including several hybrids) every 16 months; the antennas are moved every three to four months.

GALEX (Galaxy Evolution Explorer)

- an orbiting space telescope launched in 2003 that is observing galaxies in ultraviolet light across 10 billion years of cosmic history. GALEX's observations are telling scientists how galaxies, the basic structures of our Universe, evolve and change. Additionally, GALEX observations are investigating the causes of star formation during a period when most of the stars and elements we see today had their origins. GALEX is conducting several first-of-a-kind sky surveys, including an extra-galactic (beyond our galaxy) ultraviolet all-sky survey. During its mission GALEX will produce the first comprehensive map of a Universe of galaxies under construction, bringing us closer to understanding how galaxies like our own Milky Way were formed. The spacecraft has, for the first time, identified dwarf galaxies forming out of nothing more than pristine gas likely leftover from the early universe. The findings surprised astronomers because most galaxies form in association with a mysterious substance called dark matter or out of gas containing metals. this new type of dwarf galaxy may be common throughout the more distant and early universe, when pristine gas was more pervasive. Astronomers spotted the unexpected new galaxies forming inside the Leo Ring, a huge cloud of hydrogen and helium that traces a ragged path around two massive galaxies in the constellation Leo. The cloud is thought likely to be a primordial object, an ancient remnant of material that has remained relatively unchanged since the very earliest days of the universe.

Almaz

- program was a series of military space stations (or "Orbital Piloted Station" - OPS) launched by the Soviet Union under cover of the civilian Salyut DOS-17K (Orbital space station) program after 1971. Three Almaz stations were launched: Salyut 2, Salyut 3 and Salyut 5. Salyut 2 failed shortly after achieving orbit, but Salyut 3 and Salyut 5 both conducted successful manned testing. Following Salyut 5, the Soviet Ministry of Defense judged in 1978 that the time consumed by station maintenance outweighed the benefits relative to automatic reconnaissance satellites. The word 'Almaz' means 'diamond.'

Subaru Telescope

- the 8.2 metre flagship telescope of the National Astronomical Observatory of Japan, located in Mauna Kea Observatory on Hawaii. It is named after the open star cluster known in English as the Pleiades. It is a Cassegrain reflector-type telescope. The prime focus camera, rare with this class of telescope, provides wide field of view suited to the deep wide-field survey.

Deep Impact

- the first experiment to probe beneath the surface of a comet (Tempel 1), attempting to reveal never before seen materials that would provide clues to the internal composition and structure of a comet. The two-part spacecraft consisted of a larger "flyby" spacecraft carrying a smaller "impactor" spacecraft. A variety of instruments, both onboard the spacecraft and at ground-based and space-based observatories around the world, observed the impact with the comet and examined the resulting debris and interior material. Scientists learned the comet interior is well shielded from the solar heating experienced by the surface of the comet nucleus. Mission data indicate the nucleus is extremely porous, allowing the surface to heat up and cool down almost instantly in response to sunlight. This suggests heat is not easily conducted to the interior, and the ice and other material deep inside the nucleus may be pristine and unchanged from the early days of the solar system, just as many scientists had suggested. The science team was surprised to find evidence of what appear to be impact craters on the surface of the comet. Another interesting finding is the huge increase in carbon-containing molecules detected in spectral analysis of the ejection plume, indicating that comets contain a substantial amount of organic material and thus could have brought such material to Earth early in the planet's history.

SALT (Southern African Large Telescope)

- the largest optical telescope in the southern hemisphere. SALT is a ~10 meter (~33 feet) diameter optical telescope, located close to the town of Sutherland in the semi-desert region of the Karoo, South Africa. It will enable imaging, spectroscopic, and polarimetric analysis of the radiation from astronomical objects out of reach of northern hemisphere telescopes. First light with the full mirror was declared on September 1, 2005.

Buran

- the only fully completed and operational space shuttle vehicle from the Soviet Buran program. With a design that borrowed heavily from the American Space Shuttle, the Buran completed one unmanned spaceflight in 1988 before cancellation of the Soviet shuttle program in 1993. The Buran was subsequently destroyed by a hangar collapse in 2002. Like its American counterpart, the Buran, when in transit from its landing sites back to the launch complex, was transported on the back of a large jet airplane. It was piggy-backed on the Antonov An-225 Mriya aircraft, which was designed for this task and remains the largest aircraft in the world. The name 'Buran' means 'snowstorm' or 'blizzard.'

COBE (Cosmic Background Explorer)

- the purpose of the mission was to take precise measurements of the cosmic microwave background radiation, the diffuse radiation between 1 micrometer and 1 cm over the whole celestial sphere. The following quantities were measured: (1) the spectrum of the 3 K radiation over the range 100 micrometers to 1 cm; (2) the anisotropy of this radiation from 3 to 10 mm; and, (3) the spectrum and angular distribution of diffuse infrared background radiation at wavelengths from 1 to 300 micrometers. The experiment module contained the instruments and a dewar filled with 650 liters of 1.6 K liquid helium, with a conical sun shade. The instrument was launched in 1989 and operations terminated in 1993.

Compton Gamma Ray Observatory

- the second of NASA's Great Observatories. Compton, at 17 tons, was the heaviest astrophysical payload ever flown at the time of its launch in 1991 aboard the space shuttle Atlantis. Compton was safely deorbited and re-entered the Earth's atmosphere in 2000. Compton had four instruments that covered an unprecedented six decades of the electromagnetic spectrum, from 30 keV to 30 GeV. The Observatory was named in honor of Dr. Arthur Holly Compton, who won the Nobel prize in physics for work on scattering of high-energy photons by electrons - a process which is central to the gamma-ray detection techniques of all four instruments.

Giotto

ESA spacecraft that visited Halley's Comet in 1986, approaching within 596 km of the nucleus. Images showed Halley's nucleus to be a dark peanut-shaped body, 15 km long, 7 to 10 km wide. Only 10% of the surface was active, with at least three outgassing jets seen on the sunlit side. Analysis showed the comet formed 4.5 billion years ago from volatiles (mainly ice) that had condensed onto interstellar dust particles. It had remained practically unaltered since its formation. Measured volume of material ejected by Halley: 80% water, 10% carbon monoxide, 2.5% a mix of methane and ammonia.

Orion

NASA's new crew exploration vehicle. Orion is part of the Constellation Program to send human explorers back to the moon, and then onward to Mars and other destinations in the solar system. Orion will be capable of carrying crew and cargo to the space station. It will be able to rendezvous with a lunar landing module and an Earth departure stage in low-Earth orbit to carry crews to the moon and, one day, to Mars-bound vehicles assembled in low-Earth orbit. Orion will be the Earth entry vehicle for lunar and Mars returns. Orion will be similar in shape to the Apollo spacecraft, but significantly larger. The Apollo-style heat shield is the best understood shape for re-entering Earth's atmosphere, especially when returning directly from the moon. Orion will be 5 meters (16.5 feet) in diameter and have a mass of about 22.7 metric tons (25 tons). Inside, it will have more than two-and-a-half times the volume of an Apollo capsule. The larger size will allow Orion to accommodate four crew members on missions to the moon, and six on missions to the International Space Station or Mars-bound spacecraft. Orion is scheduled to fly its first missions to the space station by 2014 and carry out its first sortie to the moon by 2020. A launch abort system atop the Orion capsule will be capable of pulling the spacecraft and its crew to safety in the event of an emergency on the launch pad or at any time during ascent.

Sputnik-1

Soviet satellite that was the world's first Earth-orbiting artificial satellite. It was launched on October 4, 1957. The name 'Sputnik' means 'satellite.' The unanticipated announcement of Sputnik 1's success precipitated the Sputnik crisis in the United States and ignited the Space Race within the Cold War. Apart from its value as a technological first, Sputnik also helped to identify the upper atmospheric layer's density, through measuring the satellite's orbital changes. It also provided data on radio-signal distribution in the ionosphere. Pressurized nitrogen, in the satellite's body, provided the first opportunity for meteoroid detection. If a meteoroid penetrated the satellite's outer hull, it would be detected by the temperature data sent back to Earth.

MODIS (Moderate Resolution Imaging Spectroradiometer)

a key instrument aboard the Terra (EOS AM) and Aqua (EOS PM) satellites. Terra's orbit around the Earth is timed so that it passes from north to south across the equator in the morning, while Aqua passes south to north over the equator in the afternoon. Terra MODIS and Aqua MODIS are viewing the entire Earth's surface every 1 to 2 days, acquiring data in 36 spectral bands, or groups of wavelengths (see MODIS Technical Specifications). MODIS

Super-Kamiokande (Super-K)

a large neutrino detector in Japan. It is located 1,000 m underground and consists of a cylindrical, stainless steel tank that holds 50,000 tons of ultra-pure water. Mounted on the superstructure are over 11,000 photomultiplier tubes. A neutrino interaction with the electrons or nuclei of water can produce a charged particle that moves faster than the speed of light in water (although of course slower than the speed of light in vacuum). This creates a cone of light known as Cherenkov radiation, which is the optical equivalent to a sonic boom. The Cherenkov light is projected as a ring on the wall of the detector and recorded by the PMTs. Using the timing and charge information recorded by each PMT, the interaction vertex, ring direction and flavor of the incoming neutrino is determined. From the sharpness of the edge of the ring the type of particle can be inferred. The Super-Kamiokande Collaboration announced the first evidence of neutrino oscillation in 1998. This was the first experimental observation consistent with the theory that the neutrino has non-zero mass.

stellar occultation

a phenomenon in which an object, such as a planet or moon, passes in front of a star, obscuring it from view.

Schmidt telescope

a sky camera, which is an astronomical camera designed to provide wide fields of view with limited aberrations. It is typically used as a survey instrument, for research programs in which a large amount of sky must be covered. These include astronomical surveys, comet and asteroid searches, and nova patrols. In addition, Schmidt cameras and derivative designs are frequently used for tracking artificial earth satellites. A Schmidt telescope was at the heart of the Hipparcos satellite, which mapped the

Supernova 1054

a supernova that was widely seen and recorded by the Chinese in 1054. It is sometimes called the Crab Supernova, because its remnant is the Crab Nebula (M1). The Crab Pulsar now lies in the heart of the nebula. It was bright enough to see in daylight for 23 days. Its progenitor star was located in the Milky Way galaxy at a distance of 6,300 light years and exploded as a core-collapse supernova.

Soyuz 1

first manned Soyuz space flight, launched into orbit on April 23, 1967. It carried a single cosmonaut, Vladimir Komarov, who was killed when the spacecraft crashed during its return to Earth. This was the first in-flight fatality in the history of spaceflight. Launched at 03:35 local time, this was also the first night launch of a human space vehicle.

Apollo 8

first manned flight around the Moon, and first manned flight of the Saturn V booster rocket.

Apollo 10

first manned flight of the Lunar Module around the Moon.

Apollo 11

first manned landing on the Moon, July 20, 1969. Neil Armstrong was the commander of the mission, and the first person to set foot on the moon. Buzz Aldrin was the Lunar Module pilot, which was given the name Eagle. Aldrin was the second person to set foot on the Moon. Michael Collins was the Command Module pilot - unlike Armstrong and Aldrin, he did not land on the Moon, but instead stayed in orbit around the Moon in the Command Module, which was named Columbia. The Saturn V booster rocket launched the mission into space.

Vostok-2

first manned mission lasting a full day.

Apollo 15

first mission of the Lunar Rover vehicle.

Apollo 12

first precise manned landing on the Moon.

Mariner 3

intended to complete a Mars flyby mission, Mariner 3 was lost when the launch vehicle's nose fairing failed to jettison.

Gemini 6A and Gemini 7

launched in 1965, these missions marked the first time two spacecraft were maneuvered with respect to each other by their crews (as they orbited the Earth).

Galileo

launched in 1989, Galileo accomplished a 14-year mission to study Jupiter. list of discoveries started even before Galileo got a glimpse of Jupiter. As it crossed the asteroid belt in October 1991, Galileo snapped images of Gaspra, returning the first ever close-up image of an asteroid. Less then a year later, the spacecraft got up close to yet another asteroid, Ida, revealing it had its own little "moon," Dactyl, the first known moon of an asteroid. In 1994 the spacecraft made the only direct observation of a comet impacting a planet-- comet Shoemaker-Levy 9's collision with Jupiter. The descent probe made the first in-place studies of the planet's clouds and winds, and it furthered scientists' understanding of how Jupiter evolved. The probe also made composition measurements designed to assess the degree of evolution of Jupiter compared to the Sun. Galileo made the first observation of ammonia clouds in another planet's atmosphere. It also observed numerous large thunderstorms on Jupiter many times larger than those on Earth, with lightning strikes up to 1,000 times more powerful than on Earth. It was the first spacecraft to dwell in a giant planet's magnetosphere long enough to identify its global structure and to investigate the dynamics of Jupiter's magnetic field. Galileo determined that Jupiter's ring system is formed by dust kicked up as interplanetary meteoroids smash into the planet's four small inner moons. Galileo data showed that Jupiter's outermost ring is actually two rings, one embedded within the other. Galileo extensively investigated the geologic diversity of Jupiter's four largest moons: Ganymede, Callisto, Io and Europa. Galileo found that Io's extensive volcanic activity is 100 times greater than that found on Earth. The moon Europa, Galileo unveiled, could be hiding a salty ocean up to 100 kilometers (62 miles) deep underneath its frozen surface containing about twice as much water as all the Earth's oceans. Data also showed Ganymede and Callisto may have a liquid-saltwater layer. The biggest discovery surrounding Ganymede was the presence of a magnetic field. No other moon of any planet is known to have one.

Ulysses

launched in 1990 and still operating, Ulysses was the first mission to survey the space environment above and below the poles of the Sun. The reams of data Ulysses returned over its 17-year life forever changed the way scientists view our star and its effects on the solar system. The spacecraft's six-year orbits over the Sun's poles allowed scientists to observe our star from an unprecedented angle during both calm and turbulent periods. Ulysses made the first direct measurements of interstellar dust particles and interstellar helium atoms in the solar system and the discovery that the magnetic field leaving the sun is balanced across latitudes. The observations redefined the way scientists think about space weather. The primary mission of the Ulysses spacecraft was to characterize the heliosphere as a function of solar latitude. The heliosphere is the vast region of interplanetary space occupied by the Sun's atmosphere and dominated by the outflow of the solar wind. The periods of primary scientific interest is when Ulysses was at or higher than 70 degrees latitude at both the Sun's south and north poles. Original Ulysses Mission science objectives are to investigate for the first time as a function of heliographic latitude the properties of the solar wind, the structure of the Sun/wind interface, the heliospheric magnetic field, solar radio bursts and plasma waves, solar X-rays, solar and galactic cosmic rays, and both interstellar and interplanetary neutral gas and dust.

TOPEX/Poseidon

launched in 1992, TOPEX/Poseidon used the global perspective available only from space to develop maps of ocean topography showing the barely perceptible hills and valleys of the sea surface. TOPEX/Poseidon monitored global ocean circulation, improved global climate predictions, and tracked El Niño conditions and ocean eddies. After over 62,000 orbits, the satellite has ceased operations. TOPEX/Poseidon remains in orbit 830 miles above the Earth, posing no threat to the planet. The mission's most important achievement was to determine the patterns of ocean circulation - how heat stored in the ocean moves from one place to another. Another of the mission's major accomplishments was to develop the most accurate ever global ocean tide models. Jason, a follow-on oceanography mission launched in December 2001, is continuing TOPEX/Poseidon's study of ocean circulation and its effects on the Earth's climate. Jason precisely maps the surface height, wind speed and wave height of 95 percent of Earth's ice-free oceans every 10 days.

Wind

launched in 1994, the Wind spacecraft is the first of two U.S. missions of the Global Geospace Science (GGS) initiative, which is part of a worldwide collaboration called the International Solar-Terrestrial Physics (ISTP) program. The aim of ISTP is to understand the physical behavior of the solar-terrestrial system in order to predict how the Earth's magnetosphere and atmosphere will respond to changes in solar wind. Wind plays a crucial role -- essentially that of a scout and sentry -- in the fleet of ISTP satellites. The task of Wind is to measure crucial properties of the solar wind before it impacts the Earth's magnetic field and alters the Earth's space environment (which contains charged particles, electric and magnetic fields, electric currents and radiation) and upper atmosphere in a direct manner.

TOMS (Total Ozone Mapping Spectrometer)

launched in 1996 aboard the TOMS/EP satellite. This mission continues NASA's long-term daily mapping of the global distribution of the Earth's atmospheric ozone. TOMS/EP will again take high-resolution measurements of the total column amount of ozone from space that began with NASA's Nimbus-7 satellite in 1978 and continued with the TOMS aboard a Russian Meteor-3 satellite until the instrument stopped working in December 1994. This NASA-developed instrument measures ozone indirectly by mapping the ultraviolet light emitted by the Sun compared to that scattered from the Earth's atmosphere back to the satellite. The TOMS instrument has mapped in detail the global ozone distribution as well as the Antarctic "ozone hole," which forms September through November of each year.

TRACE (Transition Region and Coronal Explorer)

launched in 1998 and still operating today, The objective of the Transition Region and Coronal Explorer (TRACE) satellite is to explore the three-dimensional magnetic structures which emerge through the visible surface of the Sun -- the Photosphere -- and define both the geometry and dynamics of the upper solar atmosphere - the Transition Region and Corona. The magnetic field geometry can be seen in images of solar plasma taken in wavelengths emitted or absorbed by atoms and ions formed in different temperature ranges. The transition from the 6000 degree K Photosphere, where magnetic fields and plasma are in rough equipartition (low beta), to the multi-million degree Corona, where the magnetic fields dominate (high beta), is extremely difficult to model. Many of the physical process that occur here -- plasma confinement, reconnection, wave propagation, plasma heating -- arise throughout space physics and astrophysics. And to date, no images have ever been collected that show the required temperature range nearly simultaneously with both high spatial and temporal resolution. The TRACE data will provide quantitative observational constraints on the models and thus stimulate real advances in our understanding of the transition from low to high beta plasma. The solar atmosphere is constantly evolving because the magnetic fields which dominate the Corona are continuously being displaced by the convective motions in the outer layers of the Sun just below the Photosphere. A major objective of the TRACE investigation is to explore the relation between diffusion of the surface magnetic fields and the changes in heating and structure throughout the Transition Region and Corona. The simultaneous movies of the 6000 to 10,000,000 degree K volume of the solar atmosphere will allow us to determine the rate of change of the magnetic topology and the nature of the local restructuring and reconnection processes.

Mars Express

launched in 2003, NASA is participating in a mission of the European Space Agency and the Italian Space Agency called Mars Express, which has been exploring the atmosphere and surface of Mars from polar orbit since arriving at the red planet on December 26, 2003. The mission's main objective is to search for sub-surface water from orbit. Seven scientific instruments on the orbiting spacecraft have conducted rigorous investigations to help answer fundamental questions about the geology, atmosphere, surface environment, history of water, and potential for life on Mars. Examples of discoveries - still debated by scientists -- by Mars Express are evidence of recent glacial activity, explosive volcanism, and methane gas.

Mariner 9

spacecraft launched in 1971 which became the first artificial satellite of Mars. It photographed the surface and analyzed the atmosphere of Mars with its infrared and ultraviolet instruments. Its sister craft (Mariner 8) was lost in a launch vehicle failure.

IBEX (Interstellar Boundary Explorer)

spacecraft launched in 2008 to explore the termination shock, an invisible shock formed as the solar wind piles up against the gas in interstellar space. This boundary, marks the beginning of our solar system's final frontier, a vast expanse of turbulent gas and twisting magnetic fields. This region is critical because it shields out the vast majority of the deadly cosmic rays that would otherwise permeate the space around the Earth and other planets. IBEX will go beyond the Earth's magnetosphere, because this region generates radiation and the same high-speed atoms (Energetic Neutral Atoms, or ENAs) the IBEX will use to make its pictures.

VLBA (Very Long Baseline Array) - a system of ten radio telescopes controlled remotely from the Array Operations Center in Socorro, New Mexico (USA) by the National Radio Astronomy Observatory. The array works together as the world's largest dedicated, full-time astronomical instrument using the technique of very long baseline interferometry. Its construction began in February 1986, and was completed in May 1993. The first observation using all ten sites occurred in May 29, 1993. Each VLBA station consists of an 82-foot (25 m) diameter dish antenna and an adjacent control building which houses the station computer, tape recorders and other equipment associated with collecting the radio signals gathered by the antenna. Each antenna weighs 240 short tons (218 t) and is nearly as tall as a ten story building when pointed straight up. The longest baseline in the array is 8,611 kilometers (5,351 mi)

the distance from Mauna Kea in Hawaii to St. Croix (U.S. Virgin Islands). The ten radio telescopes in the array are located in Hawaii, Washington state, California, Arizona, New Mexico, Texas, Iowa, New Hampshire, and St. Croix (U.S. Virgin Islands).

heliacal rise (or heliacal rising)

the first appearance of a star before sunrise, at the start of its new season of visibility. Heliacal risings occur after a star has been behind the Sun for a season and it is just returning to visibility. There is one morning, just before dawn, when the star suddenly reappears after its absence. On that day it "blinks" on for a moment just before the sunrise and just before it is then obliterated by the Sun's presence. That one special morning is called the star's heliacal rising. Each day that passes after the heliacal rising, the star will appear to rise earlier and remain in the sky longer (that is, not blink) before its soft glow is obliterated by the rising sun.

Rosetta - a European Space Agency mission, the first to ever rendezvous with a comet, with rendezvous occurring in August 2014. The comet is called 67P/Churyumov-Gerasimenko. The main spacecraft will orbit the comet, while taking scientific measurements. A Surface Science Package (SSP) landed on the comet surface to take in-situ measurements

the lander is named Philae. The Philae lander successfully landed on November 12, 2014. NASA has contributed three instruments to Rosetta - ALICE, MIRO, and IES - plus a significant portion of the electronics package for another instrument, ROSINA. ALICE , MIRO, and IES will provide information about the dynamics of comet C-G: how it develops its coma and tails, and how its chemicals interact with each other, and with radiation and the solar wind. The comet will reach perihelion, its closest approach to the Sun, on August 13, 2015, in between the orbits of Earth and Mars. The comet has a dual-lobed shape. By assuming an overall composition dominated by water ice and dust with a density of 1500-2000 kg/m3, the Rosetta scientists show that the comet has a very high porosity of 70-80%, with the interior structure likely comprising weakly bonded ice-dust clumps with small void spaces between them. Gases escaping from the comet come mostly from the narrow 'neck' of the comet. The dusty covering of the comet may be several metres thick in places and measurements of the surface and subsurface temperature by the Microwave Instrument on the Rosetta Orbiter, or MIRO, suggest that the dust plays a key role in insulating the comet interior, helping to protect the ices thought to exist below the surface. The surface appears to be compositionally very homogenous and dominated by dust and carbon-rich molecules, but largely devoid of ice. But smaller, bright areas seen in images are likely to be ice-rich. Images from the scientific and navigation cameras have shown an increase in the amount of dust flowing away from the comet over the past six months, and MIRO showed a general rise in the comet's global water vapour production rate, from 0.3 litres per second in early June 2014 to 1.2 litres per second by late August. MIRO also found that a substantial portion of the water seen during this phase originated from the comet's neck. Water is accompanied by other outgassing species, including carbon monoxide and carbon dioxide. The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis, ROSINA, is finding large fluctuations in the composition of the coma, representing daily and perhaps seasonal variations in the major outgassing species. Water is typically the dominant outgassing molecule, but not always.By combining measurements from MIRO, ROSINA and GIADA (Rosetta's Grain Impact Analyzer and Dust Accumulator) taken between July and September, the Rosetta scientists have made a first estimate of the comet's dust-to-gas ratio, with around four times as much mass in dust being emitted than in gas, averaged over the sunlit nucleus surface.

Supernova 1987A

the only supernova explosion in modern times visible in the sky to the naked eye. It occurred in the outskirts of the Tarantula Nebula in the Large Magellanic Cloud, a nearby dwarf galaxy. It was the closest observed supernova since SN 1604, which occurred in the Milky Way itself. It occurred approximately 51.4 kiloparsecs from Earth (168,000 years ago), close enough that it was visible to the naked eye. It was the first opportunity for modern astronomers to see a supernova up close.

Mercury-Atlas 9

the spacecraft Faith 7 carried Leroy Cooper on 22 orbits, making him the first American in space for over a day.

Mercury-Redstone 3

the spacecraft Freedom 7 made Alan Shepard the first American in space. The suborbital flight lasted 15 minutes 28 seconds.

Van Allen belts

two doughnut-shaped zones of high-energy charged particles located in Earth's magnetosphere - one is located about 3000 km and the other at 20,000 km above the Earth's surface. They are called belts because they are most pronounced near the equator and because they completely surround the planet. The particles that make up the Van Allen belts originate in the solar wind. A magnetic field exerts a force on a moving charged particle, causing the particle to spiral around the magnetic field lines. In this way, charged particles (mainly electrons and protons) from the solar wind are trapped by Earth's magnetism, and are herded into the Van Allen belts. The outer belt contains mostly electrons, whereas the much heavier protons accumulate in the inner belt. Particles from these belts often escape from the magnetosphere near Earth's north and south magnetic poles, where the field lines intersect the atmosphere. Their collisions with air molecules create a spectacular light show called an aurora.

Penzias and Wilson

two scientists that, while working at Bell Labs, discovered the microwave background radiation, which supported the idea that the universe was created by the Big Bang. In 1964, on building their most sensitive antenna/receiver system, the pair encountered radio noise which they could not explain. It was far less energetic than the radiation given off by the Milky Way, and it was isotropic. This was later identified as the cosmic microwave background radiation (CMB), the radio remnant of the Big Bang. This allowed astronomers to confirm the Big Bang, and to correct many of their previous assumptions about it.

Michelson, Albert

used a stellar interferometer in 1920 to measure the diameter of Betelgeuse. This was the first diameter measurement of a star other than our Sun.

syzygy

the name given to the configuration when three celestial bodies are in a line