Process of Science: Observation Techniques, Mastering Astronomy, Astronomy 2, Chapter 6, Astro ch6, ASTR 102 Chapter 6: Telescopes: Portals of Discovery, Astronomy 101 Study Guide
axis tilt
(of a planet in our solar system) The amount by which a planet's axis is tilted with respect to a line perpendicular to the ecliptic plane.
expansion
(of the universe) The idea that the space between galaxies or clusters of galaxies is growing with time.
solar system
(or star system) A star (sometimes more than one star) and all the objects that orbit it.
If the 14 billion year history of the universe were compressed to one year, and "now" is exactly midnight December 31, approximately how long ago were your grandparents born?
0.15 second ago
Suppose a photon has a frequency of 300 million hertz (300 megahertz). What is its wavelength?
1 meter
1. The ______ of the Hubble Space Telescope is better for shorter (bluer) wavelengths of light than for longer (redder) wavelengths of light. 2.The large research observatories on Mauna Kea use giant ______ 3._____ separate the various colors of light, allowing astronomers to determine stellar composition and many other stellar properties 4.__________ separate the various colors of light, allowing astronomers to determine stellar composition and many other stellar properties 5. The Chandra X-ray observatory focuses X rays with ____ mirrors. 6. A 10-meter telescope has a larger ______ 7.Galileo's telescope designs using lenses were examples of ____
1. Angular Resolution 2. Reflecting Telescopes 3. Spectrographs 4. Interferometry 5. Grazing Incidence 6. Light-collecting area 7. Refracting Telescopes
Based on observations of the universal expansion, the age of the universe is about _________.
14 billion years
Which technology can allow a single ground-based telescope to achieve images as sharp as those from the Hubble Space Telescope?
Adaptive optics
Suppose you built a scale-model atom in which the nucleus is the size of a tennis ball. About how far would the cloud of electrons extend?
Several kilometers
On a scale in which the distance from Earth to the Sun is about 15 meters, the distance from Earth to the Moon is _________.
small enough to fit within your hand
What is the "Raisin Cake model" intended to explain?
that every raisin in a raisin cake moves farther away from every other raisin: there is no special central raisin (and no special central galaxy)
If you could count stars at a rate of about one per second, how long would it take to count all the stars in the Milky Way Galaxy?
Several thousand years
rotation
The spinning of an object around its axis. For example, Earth rotates once each day around its axis, which is an imaginary line connecting the North and South Poles.
When we look at an object that is 1,000 light-years away we see it _
as it was 1,000 years ago
When we look at an object that is 1,000 light-years away we see it _________.
as it was 1,000 years ago
Consider an atom of carbon in which the nucleus contains 6 protons and 7 neutrons. What is its atomic number and atomic mass number?
atomic number = 6; atomic mass number = 13
The term observable universe refers to
that portion of the universe that we can see in principle, given the current age of the universe
The term observable universe refers to _________.
that portion of the universe that we can see in principle, given the current age of the universe
The age of our solar system is about:
one-third of the age of the universe.
dwarf planet
orbits a star, is large enough for its own gravity to make it round
When considering light as made up of individual "pieces," each characterized by a particular amount of energy, the pieces are called _________.
photons
Thermal radiation is defined as _________.
radiation with a spectrum whose shape depends only on the temperature of the emitting object
Which of the following wavelength regions can be studied with telescopes on the ground?
radio, visible, and very limited portions of the infrared and ultraviolet regions
When your eye forms an image, the _____ plays a role analogous to the detector in a camera.
retina
galaxy cluster
see cluster of galaxies.
star system
see solar system.
Our solar system consists of _________.
the Sun and all the objects that orbit it
An astronomical unit (AU) is _________.
the average distance between Earth and the Sun
What do astronomers mean by the Big Bang?
the event that marked the beginning of the expansion of the universe
The total number of stars in the observable universe is roughly equivalent to
the number of grains of sand on all the beaches on Earth.
If we represent the solar system on a scale that allows us to walk from the Sun to Pluto in a few minutes, then:
the planets would all be marble size or smaller and the nearest stars would be thousands of miles away.
The total number of stars in the observable universe is about
the same as the number of grains of sand on all the beaches on Earth
The total number of stars in the observable universe is about _________.
the same as the number of grains of sand on all the beaches on Earth
Our solar system consists of
the sun and all the objects that orbit it
Suppose you want to know the chemical composition of a distant star. Which piece of information is most useful to you?
the wavelengths of spectral lines in the star's spectrum
The stars in our sky twinkle in brightness and color because of ______.
turbulence in the Earth's atmosphere
Which of the following effects is caused by atmospheric turbulence?
twinkling of stars
Suppose we look at two distant galaxies: Galaxy 1 is twice as far away as Galaxy 2. In that case _________.
we are seeing Galaxy 1 as it looked at an earlier time in the history of the universe than Galaxy 2
The star Betelgeuse is about 600 light-years away. If it explodes tonight,
we won't know about it until 600 years from now.
Gamma rays have a very small ______.
wavelength
Suppose we look at two distant galaxies: Galaxy 1 is twice as far away as Galaxy 2. In that case
we are seeing Galaxy 1 as it looked at an earlier time in the history of the universe than Galaxy 2
The diffraction limit is a limit on ...
A telescope's angular resolution.
expansion (of the universe)
The increase in the average distance between galaxies as time progresses.
Sublimation is the process in which ___________.
molecules go directly from the solid phase to the gas phase
An atom which has 4 protons and 6 neutrons will be electrically neutral if it contains ______.
4 electrons
Suppose you have a 100-watt light bulb that you leave turned on for one minute. How much energy does it use?
6,000 joules
cluster of galaxies
A collection of a few dozen or more galaxies bound together by gravity; smaller collections of galaxies are simply called groups.
cluster of galaxies (or group of galaxies)
A collection of galaxies bound together by gravity. Small collections (up to a few dozen galaxies) are generally called groups, while larger collections are called clusters.
group (of galaxies)
A few to a few dozen galaxies bound together by gravity. see also cluster of galaxies.
supercluster
A gigantic region of space in which many groups and clusters of galaxies are packed more closely together than elsewhere in the universe.
galaxy
A great island of stars in space, all held together by gravity and orbiting a common center, with a total mass equivalent to millions, billions, or even trillions of stars.
galaxy
A great island of stars in space, containing millions, billions, or even trillions of stars, all held together by gravity and orbiting a common center.
Which of the following statements about thermal radiation is always true?
A hot object emits more radiation per unit surface area than a cool object.
star
A large, glowing ball of gas that generates energy through nuclear fusion in its core. The term star is sometimes applied to objects that are in the process of becoming true stars (e.g., protostars) and to the remains of stars that have died (e.g., neutron stars).
star
A large, glowing ball of gas that generates heat and light through nuclear fusion in its core. Our Sun is a star.
planet
A moderately large object that orbits a star and shines primarily by reflecting light from its star. According to the current definition, an object can be considered a planet only if it orbits a star, is large enough for its own gravity to make it round, and has cleared most other objects from its orbital path.
planet
A moderately large object that orbits a star and shines primarily by reflecting light from its star. More precisely, according to a definition approved in 2006, a planet is an object that (1) orbits a star (but is itself neither a star nor a moon); (2) is massive enough for its own gravity to give it a nearly round shape; and (3) has cleared the neighborhood around its orbit. Objects that meet the first two criteria but not the third, including Ceres, Pluto, and Eris, are designated dwarf planets.
Which of the following statements best describes the difference between a refracting telescope and a reflecting telescope?
A refracting telescope uses a transparent glass lens to focus light while a reflecting telescope uses a mirror to focus light
comet
A relatively small and ice-rich object that orbits a star.
asteroid
A relatively small and rocky object that orbits a star.
asteroid
A relatively small and rocky object that orbits a star; asteroids are officially considered part of a category known as "small solar system bodies."
comet
A relatively small, icy object that orbits a star. Like asteroids, comets are officially considered part of a category known as "small solar system bodies."
star system
A star (sometimes more than one star) and any planets and other materials that orbit it.
Which of the following statements best describes the difference between a refracting telescope and a reflecting telescope? A) A refracting telescope uses a transparent glass lens to focus light while a reflecting telescope uses a mirror to focus light. B) A refracting telescope produces refracted images while a reflecting telescope produces reflected images. C) Reflecting telescopes make much clearer images than can refracting telescopes of the same size. D) It is much easier to make a large refracting telescope than a large reflecting telescope.
A) A refracting telescope uses a transparent glass lens to focus light while a reflecting telescope uses a mirror to focus light.
Which of the following best describes why radio telescopes are generally much larger in size than telescopes designed to collect visible light? A) Getting an image of the same angular resolution requires a much larger telescope for radio waves than for visible light. B) Radio telescopes are designed to collect sound rather than light. C) It is because radio telescopes are used in the daytime and visible light telescopes are used at night. D) Objects that emit radio waves are always much larger than objects that emit visible light, and therefore require larger telescopes.
A) Getting an image of the same angular resolution requires a much larger telescope for radio waves than for visible light.
What is the purpose of interferometry? A) It allows two or more small telescopes to achieve the angular resolution of a much larger telescope. B) It allows two or more small telescopes to achieve a larger light-collecting area than they would have independently . C) t is designed to prevent light pollution from interfering with astronomical observations. D) It reduces the twinkling of stars caused by atmospheric turbulence.
A) It allows two or more small telescopes to achieve the angular resolution of a much larger telescope.
What is a CCD? A) It is an electronic detector that can be used in place of photographic film for making images. B) It is an abbreviation for the world's largest operating telescope. C) It refers to any kind of instrument that can be hooked up to a telescope. D) It is a unit used by astronomers to measure angular resolution.
A) It is an electronic detector that can be used in place of photographic film for making images.
Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes? A) It is closer to the stars. B) Stars do not twinkle when observed from space. C) It can observe infrared and ultraviolet light, as well as visible light. D) It never has to close because of bad weather. E) Observers on the ground can use it at any time of day (i.e., not only during their night).
A) It is closer to the stars.
Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes? A) It is closer to the stars. B) Stars do not twinkle when observed from space. C) It can observe infrared and ultraviolet light, as well as visible light. D) It never has to close because of cloudy skies.
A) It is closer to the stars.
What is the purpose of adaptive optics? A) It reduces blurring caused by atmospheric turbulence for telescopes on the ground. B) It allows several small telescopes to work together like a single larger telescope. C) It is a special technology that allows the Hubble Space Telescope to adapt to study many different types of astronomical objects. D) It allows ground-based telescopes to observe ultraviolet light that normally does not penetrate the atmosphere.
A) It reduces blurring caused by atmospheric turbulence for telescopes on the ground.
Consider two future observatories in space. Observatory X consists of a single 50-meter telescope. Observatory Y is an interferometer consisting of five 10-meter telescopes, spread out over a region 100 meters across. Which observatory can detect dimmer stars, and which one can see more detail in its images? (Assume all else is equal, such as quality of optics, types of instruments, and so on.) A) Observatory X can detect dimmer stars and Observatory Y reveals more detail in images. B) Observatory Y can detect dimmer stars and Observatory X reveals more detail in images. C) Observatory X both detects dimmer stars and reveals more detail in images. D) Observatory Y both detects dimmer stars and reveals more detail in images.
A) Observatory X can detect dimmer stars and Observatory Y reveals more detail in images.
Which of the following statements best describes the two principal advantages of telescopes over eyes? A) Telescopes can collect far more light with far better angular resolution. B) Telescopes can collect far more light with far greater magnification. C) Telescopes have much more magnification and better angular resolution. D) Telescopes collect more light and are unaffected by twinkling. E) Telescopes can see farther without image distortion and can record more accurate colors.
A) Telescopes can collect far more light with far better angular resolution.
Which of the following statements best describes the two principle advantages of telescopes over eyes? A) Telescopes can collect far more light with far better angular resolution. B) Telescopes can collect far more light with far greater magnification. C) Telescopes collect more light and are unaffected by twinkling. D) Telescopes have much more magnification and better angular resolution.
A) Telescopes can collect far more light with far better angular resolution.
Which of the following is not a major reason why astronomers would like an observatory on the far side of the Moon? A) Telescopes on the Moon could see objects in all parts of the sky equally well, whereas telescopes on Earth can see only portions of the sky that depend on their latitude. B) Radio astronomy would be advantageous on the Moon because human radio transmissions are less likely to cause interference, especially on the far side of the Moon. C) It would be possible to put telescopes for ultraviolet and X-ray astronomy on the surface, unlike the case on the surface of the Earth. D) Telescopes on the Moon could observe stars even when it is daytime on the Moon.
A) Telescopes on the Moon could see objects in all parts of the sky equally well, whereas telescopes on Earth can see only portions of the sky that depend on their latitude.
How does the light-collecting area of an 8-meter telescope compare to that of a 2-meter telescope? A) The 8-meter telescope has 16 times the light-collecting area of the 2-meter telescope. B) The 8-meter telescope has 4 times the light-collecting area of the 2-meter telescope. C) The 8-meter telescope has 8 times the light-collecting area of the 2-meter telescope. D) The answer cannot be determined from the information given in the question.
A) The 8-meter telescope has 16 times the light-collecting area of the 2-meter telescope.
Which of the following telescopes would benefit most from adaptive optics? A) The Keck I Telescope on Mauna Kea. B) The Hubble Space Telescope. C) The Arecibo Radio Telescope in Puerto Rico. D) The Chandra X-Ray Observatory.
A) The Keck I Telescope on Mauna Kea.
Suppose you have two small photographs of the Moon. Although both look the same at small size, when you blow them up to poster size one of them still looks sharp while the other one becomes fuzzy (grainy) looking. Which of the following statements is true? A) The one that still looks sharp at large size has better (smaller) angular resolution than the one that looks fuzzy . B) The one that looks fuzzy at large size has better angular resolution (smaller) than the one that looks sharp. C) Both photographs have the same angular resolution, because they were both printed at the same sizes in each case. D) Both photographs have the same angular resolution, because they are both photographs of the same object.
A) The one that still looks sharp at large size has better (smaller) angular resolution than the one that looks fuzzy .
Suppose you point your telescope at a distant object. Which of the following is not an advantage of taking a photograph of the object through the telescope as compared to just looking at the object through the telescope? A) The photograph will have far better angular resolution than you can see with your eye. B) By using a long exposure time, the photograph can allow you to see objects that would be too dim to see with your eye. C) If taken with a camera with a sensitive detector such as a CCD, the photograph can capture a much larger percentage of the incoming photons than can your eye. D) The photograph provides a more reliable record of what is seen through the telescope than can a drawing made by eye.
A) The photograph will have far better angular resolution than you can see with your eye.
Which of the following is not a reason why telescopes tend to be built on mountaintops that are relatively far from cities and are in regions with dry climates? A) The thin air on mountaintops makes the glass in telescope mirrors less susceptible to warping. B) Being on a high mountain top means being relatively high in the atmosphere, which tends to limit turbulence. C) Dry regions mean less rain and clouds, and mountaintops in dry regions may even allow some infrared observations. D) Mountaintops far from cities are generally subject to less light pollution than locations nearer to cities.
A) The thin air on mountaintops makes the glass in telescope mirrors less susceptible to warping.
Which of the following is always true about images captured with X-ray telescopes? A) They are always shown with colors that are not the true colors of the objects that were photographed. B) They always are made with adaptive optics. C) They show us light with extremely long wavelengths compared to the wavelengths of visible light. D) They always have very high angular resolution. E) They are always very pretty.
A) They are always shown with colors that are not the true colors of the objects that were photographed.
What is an artificial star? A) a point of light in Earth's atmosphere created by a laser for the purpose of monitoring atmospheric fluctuations B) a satellite orbiting Earth C) a meteor D) a possible source of dark matter in the universe E) the unseen member of a binary star system
A) a point of light in Earth's atmosphere created by a laser for the purpose of monitoring atmospheric fluctuations
Order the following in order of increasing efficiency of detecting photons of visible light. A) eye, photographic film, CCD B) photographic film, CCD, eye C) CCD, eye, photographic film D) CCD, photographic film, eye E) eye, CCD, photographic film
A) eye, photographic film, CCD
Which of the following is not one of the three main categories of observation generally used by astronomers? A) filtering to look at just a single color from an object B) timing to track how an object's brightness varies with time C) spectroscopy to spread an object's light into a spectrum D) imaging to get a picture of an astronomical objects
A) filtering to look at just a single color from an object
At which wavelength range is there no current or planned space observatory? A) radio B) infrared C) visible D) X-ray E) gamma-ray
A) radio
In what part of the electromagnetic spectrum do the biggest telescopes on Earth operate? A) radio B) infrared C) visible D) ultraviolet E) X-ray
A) radio
In what wavelength range was interferometry first routinely used? A) radio B) infrared C) optical D) ultraviolet E) X-ray
A) radio
Which of the following wavelength regions can be studied with telescopes on the ground? A) radio, visible, and very limited portions of the infrared and ultraviolet regions B) all light with wavelengths longer than ultraviolet wavelengths C) all light with wavelengths shorter than infrared wavelengths D) infrared, visible, and ultraviolet light
A) radio, visible, and very limited portions of the infrared and ultraviolet regions
What does angular resolution measure? A) the angular size of the smallest features that the telescope can see B) the brightness of an image C) the size of an image D) the number of electromagnetic waves captured by an image
A) the angular size of the smallest features that the telescope can see
Which of the following could not be measured by an observation that uses only imaging? A) the rate at which a variable star brightens and dims B) the general shape of an interstellar cloud of gas C) the color of a planet D) the brightness of a star in our sky E) the number of bright stars in a nearby star cluster
A) the rate at which a variable star brightens and dims
The stars in our sky twinkle in brightness and color because of ________. A) turbulence in the Earth's atmosphere B) rapid changes in the brightnesses and colors of stars caused by changes in their spectra C) light pollution D) the bubbling and boiling of gases on the surfaces of stars
A) turbulence in the Earth's atmosphere
Which of the following effects is caused by atmospheric turbulence? A) twinkling of stars B) light pollution C) magnification of images D) diffraction of light
A) twinkling of stars
On a scale where the Sun is about the size of a grapefruit and the Earth is about 15 meters away, how far away are the nearest stars besides the Sun?
About the distance across the United States
The Hubble Space Telescope obtains higher-resolution images than most ground-based telescopes because it is ...
Above Earth's atmosphere.
Which of the following is not a general difference between a planet and a star?
All planets are made of rock and all stars are made of gas.
The orbital plane of the Moon is tilted slightly (by about 5 degrees) to the ecliptic plane.
All the following statements are true. Which one explains the reason that there is not a solar eclipse at every new moon?
cosmos
An alternative name for the universe.
less than the thickness of a human hair held at arm's length
An angle of 1 arcsecond is _________.
Interferometry uses two or more telescopes to achieve ...
An angular resolution equivalent to that of a much larger telescope.
small solar system body
An asteroid, comet, or other object that orbits a star but is too small to qualify as a planet or dwarf planet.
Which of the following transitions within an atom is not possible?
An electron begins in an excited state and then gains enough energy to jump to the ground state.
Suppose you look at a spectrum of visible light by looking through a prism or diffraction grating. How can you decide whether it is an emission line spectrum or an absorption line spectrum?
An emission line spectrum consists of bright lines on a dark background, while an absorption line spectrum consists of dark lines on a rainbow background.
moon
An object that orbits a planet.
moon (or satellite)
An object that orbits a planet. The term satellite is also used more generally to refer to any object orbiting another object.
satellite
Any object orbiting another object.
superclusters
The largest known structures in the universe, consisting of many clusters of galaxies, groups of galaxies, and individual galaxies.
Each of the following describes an "Atom 1" and an "Atom 2." In which case are the two atoms different isotopes of the same element?
Atom 1: nucleus with 7 protons and 8 neutrons, surrounded by 7 electrons; Atom 2: nucleus with 7 protons and 7 neutrons, surrounded by 7 electrons
What do we mean when we say that the universe is expanding?
Average distances between galaxies are increasing with time.
Which of the following best describes the principle advantage of CCDs over photographic film? A) CCDs allow long exposures (e.g., minutes or hours) and film does not. B) CCDs capture a much higher percentage of the incoming photons than film. C) CCDs can record the colors of astronomical objects accurately while film cannot. D) CCDs can be attached to modern telescopes more easily than can photographic film.
B) CCDs capture a much higher percentage of the incoming photons than film.
What does the technique of interferometry allow? A) It allows two or more telescopes to obtain a total light-collecting area much larger than the total light- collecting area of the individual telescopes. B) It allows two or more telescopes to obtain the angular resolution of a single telescope much larger than any of the individual telescopes. C) It allows us to determine the chemical composition of stars. D) It allows astronomers to make astronomical observations without interference from light pollution. E) It allows the same telescope to make images with both radio waves and visible light.
B) It allows two or more telescopes to obtain the angular resolution of a single telescope much larger than any of the individual telescopes.
What is meant by spectral resolution? A) It is a measure of how much energy an object emits in different parts of the electromagnetic spectrum. B) It is a measure of how close two spectral lines can be distinguished. C) It is a measure of how close two point sources can be distinguished. D) It is the same as angular resolution when applied to telescopes operating at different wavelengths.
B) It is a measure of how close two spectral lines can be distinguished.
What do we mean by the diffraction limit of a telescope? A) It describes the farthest distance to which the telescope can see. B) It is the angular resolution the telescope could achieve if nothing besides the size of its light-collecting area affected the quality of its images. C) It is the maximum size to which any telescope can be built. D) It describes the maximum exposure time for images captured with the telescope.
B) It is the angular resolution the telescope could achieve if nothing besides the size of its light-collecting area affected the quality of its images.
Which of the following best describes what we mean by the focal plane of a telescope? A) It is the upper surface of the telescope's primary lens or mirror. B) It is the place where, if we mounted film or an electronic detector, we could get a clear (not blurry) image of an object viewed through the telescope. C) It is the lower surface of the telescope's primary lens or mirror. D) It is the surface of the lens on the eyepiece, through which you would look to see objects in the telescope's field of view.
B) It is the place where, if we mounted film or an electronic detector, we could get a clear (not blurry) image of an object viewed through the telescope.
What is the angular resolution of the human eye? A) about 1 degree B) about 1 arcsecond (1/3600 of a degree) C) about 1 arcminute, or 1/60 of a degree D) about 1 milliarcsecond
C) about 1 arcminute, or 1/60 of a degree
What do astronomers mean by light pollution? A) Light pollution is a type of air pollution created by lightweight gases such as hydrogen and helium. B) Light pollution is light from human sources that makes it difficult to see the stars at night. C) Light pollution means contamination of light caused by chemicals in the Earth's atmosphere. D) Light pollution is a term used to describe the appearance of the sky in regions that are crowded with stars.
B) Light pollution is light from human sources that makes it difficult to see the stars at night.
Suppose the angular separation of two stars is smaller than the angular resolution of your eyes. How will the stars appear to your eyes? A) You will not be able to see these two stars at all. B) The two stars will look like a single point of light. C) The two stars will appear to be touching, looking rather like a small dumbbell. D) You will see two distinct stars. E) You will see only the larger of the two stars, not the smaller one.
B) The two stars will look like a single point of light.
The Chandra X-Ray Observatory must operate in space because: A) X rays are too dangerous to be allowed on the ground. B) X rays do not penetrate Earth's atmosphere. C) X-ray telescopes require the use of grazing incidence mirrors. D) It was built by NASA.
B) X rays do not penetrate Earth's atmosphere.
Telescopes operating at this wavelength must be cooled to observe faint astronomical objects. A) radio B) extreme infrared C) visible D) X-ray E) gamma-ray
B) extreme infrared
Which of the following studies is best suited to astronomical observations that fall into the category called timing? A) studying how different planets differ in their surface compositions B) studying how a star's brightness varies over a period of 3 years C) measuring the rotation rate of a distant star D) determining the age of the solar system
B) studying how a star's brightness varies over a period of 3 years
Which of the following studies is best suited to a timing experiment? A) studying how different stars differ in their chemical compositions B) studying whether a particular star's brightness is steady or variable C) determining the age of the solar system D) measuring the rotation rate of a distant star E) estimating the time since the Big Bang
B) studying whether a particular star's brightness is steady or variable
What is the purpose of adaptive optics? A) to improve the angular resolution of telescopes in space B) to eliminate the distorting effects of atmospheric turbulence for telescopes on the ground C) to increase the collecting area of telescopes on the ground D) to increase the magnification of telescopes on the ground E) to allow several small telescopes to work together like a single larger telescope
B) to eliminate the distorting effects of atmospheric turbulence for telescopes on the ground
Why do the patterns of the stars in our sky look the same from year to year?
Because the stars in the constellations are so far away.
Which of the following is a principal advantage of CCDs over photographic film? A) CCDs allow long exposures (e.g., minutes or hours), and film does not. B) CCDs can record the colors of astronomical objects accurately, while film cannot. C) CCDs capture a much higher percentage of the incoming photons than does film. D) Images recorded with CCDs never require any image processing, while images recorded by film often do. E) CCDs can be attached to modern telescopes more easily than cameras.
C) CCDs capture a much higher percentage of the incoming photons than does film.
What do astronomers mean by light pollution? A) Light pollution refers to pollution caused by light industry as opposed to heavy industry. B) Light pollution refers to harmful gases emitted by common street lights. C) Light pollution refers to light used for human activities that brightens the sky and hinders astronomical observations. D) Light pollution refers to the lights that must be used inside major observatories and that make it difficult for astronomers' eyes to adapt to darkness. E) Light pollution is another name for sunlight, which makes it impossible to see stars in the daytime.
C) Light pollution refers to light used for human activities that brightens the sky and hinders astronomical observations.
Why do astronomers need different telescope designs to observe across the electromagnetic spectrum? A) New telescopes incorporate new technology to increase their efficiency. B) Telescopes have to adapt to the greater distortion of the atmosphere at shorter wavelengths. C) Photons of different energy behave differently and require different collection strategies. D) Light pollution is worse at radio wavelengths than visible wavelengths. E) Astronomers and engineers enjoy the challenge of making new telescope designs.
C) Photons of different energy behave differently and require different collection strategies.
The angular separation of two stars is 0.1 arcseconds and you photograph them with a telescope that has an angular resolution of 1 arcsecond. What will you see? A) The two stars will appear to be touching, looking rather like a small dumbbell. B) The stars will not show up at all in your photograph. C) The photo will seem to show only one star rather than two. D) You will see two distinct stars in your photograph.
C) The photo will seem to show only one star rather than two.
Which of the following best describes the development of astronomical telescopes over the past 60 years? A) Over the 60-year period, telescopes have gradually gotten bigger and more powerful. B) Although there have been advances in cameras and computing power, telescopes themselves have not changed much in the last 60 years. C) The world's most powerful telescope remained the same for most of this period, but in the past 20 years many new and more powerful telescopes have been built. D) The only major change in telescope power has occurred because of our ability to launch telescopes into space rather than operating them only from the ground.
C) The world's most powerful telescope remained the same for most of this period, but in the past 20 years many new and more powerful telescopes have been built.
Consider an atom of oxygen in which the nucleus contains 8 protons and 8 neutrons. If it is doubly ionized, what is the charge of the oxygen ion and how many electrons remain in the ion?
Charge = +2; number of remaining electrons = 6.
Currently, the largest optical telescope mirrors have a diameter of A) 1 m. B) 2 m. C) 5 m. D) 10 m. E) 100 m.
D) 10 m.
What do we mean by the diffraction limit of a telescope? A) It is the maximum size to which any telescope can be built. B) It describes the farthest distance to which the telescope can see. C) It describes the maximum exposure time for images captured with the telescope. D) It is the best angular resolution the telescope could achieve with perfect optical quality and in the absence of atmospheric distortion.
D) It is the best angular resolution the telescope could achieve with perfect optical quality and in the absence of atmospheric distortion.
Which of the following statements about light focusing is not true? A) In a healthy eye, light is focused on the retina. B) Film should be placed at the focal plane in a camera. C) If you try to look at an image that is not formed at the focal plane, it will be blurry. D) The focal plane of a reflecting telescope is always located within a few inches of the primary mirror.
D) The focal plane of a reflecting telescope is always located within a few inches of the primary mirror.
Which of the following is always true about images captured with X-ray telescopes? A) They are always very pretty. B) They are always displayed with the highest possible angular resolution. C) They are always useful for seeing through things. D) They are always displayed in false color. E) They are always displayed with north pointing upward in the images.
D) They are always displayed in false color.
What causes stars to twinkle? A) It is intrinsic to the stars—their brightness varies as they expand and contract. B) variations in the absorption of the atmosphere C) variable absorption by interstellar gas along the line of sight to the star D) bending of light rays by turbulent layers in the atmosphere E) the inability of the human eye to see faint objects
D) bending of light rays by turbulent layers in the atmosphere
Which of the following wavelength regions cannot be studied with telescopes on the ground? A) radio waves B) ultraviolet C) X rays D) both B and C E) both A and C
D) both B and C
Suppose you want to determine the chemical composition of a distant planet or star. Which of the following will be most useful to have? A) high angular resolution B) high turbulence C) a radio telescope D) high spectral resolution
D) high spectral resolution
Which of the following is not a good reason to place observatories on remote mountain tops? A) to reduce light pollution B) to reduce light distortion C) to reduce light absorption D) to be able to observe at radio wavelengths E) to be able to observe at infrared wavelengths
D) to be able to observe at radio wavelengths
Earth is catching up with and passing by Mars in their respective orbits.
During the period each year when we see Mars undergoing apparent retrograde motion in our sky, what is really going on in space?
The largest effective telescope, created by radio interferometry, is the size of A) several football fields, in a natural depression in Puerto Rico. B) tens of miles across, in the deserts of New Mexico. C) the state of New Mexico. D) the continental United States. E) Earth.
E) Earth.
Which of the following could not be determined by an observation that uses only spectroscopy? A) the chemical composition of a distant star B) the speed at which a distant galaxy is moving away from us C) the surface temperature of a distant star D) the rotation rate of a distant star E) the size of a distant galaxy
E) the size of a distant galaxy
An astronomical unit is
Earth's average distance from the Sun
How do the speeds at which we are moving with Earth's rotation and orbit compare to the speeds of more familiar objects?
Earth's rotation carries most people around the axis faster than a commercial jet travels, and Earth's orbit carries us around the Sun faster than the Space Shuttle orbits Earth.
Which of the following correctly lists our "cosmic address" from small to large?
Earth, solar system, Milky Way Galaxy, Local Group, Local Supercluster, universe
Which of the following statements about electrons is not true?
Electrons orbit the nucleus rather like planets orbiting the Sun.
Professional astronomical telescopes generally have a much greater magnification than the telescopes you can buy in stores.
False
Which of the following is not one of the three main categories of observation generally used by astronomers?
Filtering to look at just a single color from an object.
Earth is stationary at the center of the universe
For most of history, the lack of observable stellar parallax was interpreted to mean that _________.
How much greater is the light-collecting area of a 6-meter telescope than a 3-meter telescope?
Four times
How are galaxies important to our existence?
Galaxies recycle material from one generation of stars to the next, and without this recycling we could not exist.
Suppose you want to determine the chemical composition of a distant planet or star. Which of the following will be most useful to have?
High spectral resolution.
It doesn't --- Earth's orbital distance plays no significant role in the seasons.
How does Earth's varying distance from the Sun affect our seasons?
the four seasons would each be twice as long as they are now
If our year were twice as long (that is, if Earth took twice as many days to complete each orbit around the Sun), but Earth's rotation period and axis tilt were unchanged, then _________.
Part A Sort each of the astronomical questions below into the appropriate bin based on the type of observation you would need to perform to answer it.
Imaging: How large is the Andromeda Galaxy? What are the major surface features of Mars? Are stars in the Orion Nebula surrounded by gas? Spectroscopy: What is the chemical composition of the Crab Nebula? What is the temperature of Jupiter's atmosphere? Is the star Vega moving toward us or away from us? Timing: Does the star Mira vary in brightness? Is the X-ray emission from the galactic center steady or changing?
Where should you put a telescope designed for ultraviolet observations?
In Earth orbit
our evening view of space depends on where Earth is located in its orbit around the Sun
In any particular place on Earth, certain constellations are visible in the evening only at certain times of the year because _________.
Part B Each of the following statements describes an astronomical measurement. Place each measurement into the appropriate bin based on the type of telescope you would use to make it.
Infrared telescope: Determine the surface temperature of Venus. Steady a dense cloud of cold gas in space. Visible Light telescope: Obtain a spectrum of the sunlight reflected by Mars. Measure the brightness of a star that is similar to our Sun. X-ray telescope: Observe the hot (1-million K) gas in the Sun's corona. Look for high-energy radiation from a supernova.
Which of the following statements is true of green grass?
It absorbs red light and reflects green light.
What is the purpose of interferometry?
It allows two or more small telescopes to achieve the angular resolution of a much larger telescope
What is the purpose of adaptive optics?
It reduces blurring caused by atmospheric turbulence for telescopes on the ground.
If you see the color red in an X-ray image from the Chandra X-Ray Observatory, it means ...
It depends: the colors are chosen arbitrarily to represent something about the X rays recorded by the telescope
Relative to the age of the universe, how old is our solar system?
It is about one-third the age of the universe.
Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes?
It is closer to the stars.
What do we mean by the diffraction limit of a telescope?
It is the angular resolution the telescope could achieve if nothing besides the size of its light-collecting area affected the quality of its images.
Which of the following best describes what we mean by the focal plane of a telescope?
It is the place where, if we mounted film or an electronic detector, we could get a clear (not blurry) image of an object viewed through the telescope.
Suppose you had molecular oxygen (O2) chilled enough so that it was in liquid form. Which of the following best describes the phase changes that would occur as you heated the liquid oxygen to high temperature?
It would evaporate into a gas, then the molecules would dissociate into individual oxygen atoms, then the atoms would become increasingly ionized as you continued to raise the temperature.
third quarter
It's 6 am and the Moon is at its highest point in your sky (crossing the meridian). What is the Moon's phase?
Betelgeuse is the bright red star representing the left shoulder of the constellation Orion. All the following statements about Betelgeuse are true. Which one can you infer from its red color?
Its surface is cooler than the surface of the Sun.
What do astronomers mean by light pollution?
Light pollution is light from human sources that makes it difficult to see the stars at night.
dark matter
Matter that we infer to exist from its gravitational effects but from which we have not detected any light; dark matter apparently dominates the total mass of the universe.
The twinkling of stars is caused by ...
Motion of air in our atmosphere.
If you wanted a radio telescope to achieve the same angular resolution as a visible-light telescope, it would need to be ...
Much larger
dark energy
Name sometimes given to energy that could be causing the expansion of the universe to accelerate. see cosmological constant.
Using the ideas discussed in your textbook, in what sense are we "star stuff"?
Nearly every atom from which we are made was once inside of a star.
Could we see a galaxy that is 20 billion light-years away? (Assume that we mean a "lookback time" of 20 billion years.)
No, because it would be beyond the bounds of our observable universe.
Could we see a galaxy that is 50 billion light-years away?
No, because it would be beyond the bounds of our observable universe.
Where is our solar system located within the Milky Way Galaxy?
Roughly halfway between the center and the edge of the visible disk of the galaxy
Consider two future observatories in space. Observatory X consists of a single 50-meter telescope. Observatory Y is an interferometer consisting of five 10-meter telescopes, spread out over a region 100 meters across. Which observatory can detect dimmer stars, and which one can see more detail in its images? (Assume all else is equal, such as quality of optics, types of instruments, and so on.
Observatory X can detect dimmer stars and Observatory Y reveals more detail in images.
Suppose that two stars are separated in the sky by 0.1 arcsecond. If you look at them with a telescope that has an angular resolution of 0.5 arcsecond, what will you see?
One point of light that is the blurred image of both stars.
How long does it take the Earth to complete one orbit around the Sun?
One year
What is the difference between energy and power?
Power is the rate at which energy is used, so its units are a unit of energy divided by a unit of time.
Suppose that Star X and Star Y both have redshifts, but Star X has a larger redshift than Star Y. What can you conclude?
Star X is moving away from us faster than Star Y.
Which of the following is a general difference between a planet and a star?
Stars glow in infrared and visible light, while planets glow only in the infrared.
Which of the following studies is best suited to astronomical observations that fall into the category called time monitoring?
Studying how a star's brightness varies over a period of 3 years.
The length of each season (for example, the number of days from the summer solstice to the fall equinox) would be significantly longer than it is now.
Suppose Earth's axis tilt was significantly greater than its current 23.5 degrees, but Earth's rotation period and orbital period were unchanged. Which statement below would not be true?
new Earth
Suppose it is full Moon. What phase of Earth would someone on the Moon see at this time?
To the right of Polaris; that is, 90 degrees counterclockwise from its current position
Suppose you are facing north and you see the Big Dipper close to your northern horizon, with Polaris (and the Little Dipper) above it. Where will you see the Big Dipper in six hours?
Your friend will also see a crescent moon.
Suppose you live in the United States and you see a crescent moon in your evening sky tonight. What will a friend in South America see tonight?
the Galileo spacecraft that orbited Jupiter in the 1990s
Suppose you see a photo showing Jupiter half in sunlight and half in shadow (that is, a first quarter Jupiter). This photo might have been taken by _________.
latitude 40 degrees south
Suppose you use the Southern Cross to determine that the south celestial pole appears 40 degrees above your horizon. Then you must be located at _________.
Which of the following statements best describes the two principle advantages of telescopes over eyes?
Telescopes can collect far more light with far better angular resolution.
We could not see it at all.
The Andromeda Galaxy is faintly visible to the naked eye in the constellation Andromeda. Suppose instead it were located in the same direction in space as the center of the Milky Way Galaxy (but still at its current distance). How would it appear to the eye in that case?
Which of the following telescopes benefits most from adaptive optics?
The Keck I telescope on Mauna Kea
the spring and fall equinoxes
The Sun's path, as viewed from the equator, is highest in the sky on _________.
What does angular resolution measure?
The angular size of the smallest features that the telescope can see.
astronomical unit (au)
The average distance (semimajor axis) of Earth from the Sun, which is about 150 million km.
astronomical unit (AU)
The average distance between Earth and the Sun, which is about 150 million kilometers. More technically, 1 AU is the length of the semimajor axis of Earth's orbit.
When we say the universe is expanding, we mean that:
The average distance between galaxies is growing with time
Which of the following conditions lead you to see an absorption line spectrum from a cloud of gas in interstellar space?
The cloud is cool and lies between you and a hot star.
light-year (ly)
The distance that light can travel in 1 year, which is 9.46 trillion km.
light-year
The distance that light can travel in 1 year, which is about 10 trillion kilometers (more precisely, 9.46 trillion km).
Suppose that two stars are identical in every way - for example, same distance, same mass, same temperature, same chemical composition, and same speed relative to Earth - except that one star rotates faster than the other. Spectroscopically, how could you tell the stars apart?
The faster rotating star has wider spectral lines than the slower rotating star.
You observe a distant galaxy. You find that a spectral line of hydrogen that is shifted from its normal location in the visible part of the spectrum into the infrared part of the spectrum. What can you conclude?
The galaxy is moving away from you.
local group
The group of about 40 galaxies to which the Milky Way Galaxy belongs.
Which statement about motion in the universe is not true?
The mysterious dark matter is the fastest-moving material in the universe.
big bang
The name given to the event thought to mark the birth of the universe.
Put the following into perspective: the size of our solar system; the distance to nearby stars; the size of the Milky Way Galaxy; the size of the observable universe. Rank from largest to smallest. To rank items as equivalent, overlap them.
The observable universe, The Milky Way Galaxy, Distances to nearby stars, solar system
orbit (or revolution)
The orbital motion of one object around another due to gravity. For example, Earth orbits the Sun once each year.
revolution
The orbital motion of one object around another.
Which of the following best describes why we say that light is an electromagnetic wave?
The passage of a light wave can cause electrically charged particles to move up and down.
orbit
The path followed by a celestial body because of gravity; an orbit may be bound (elliptical) or unbound (parabolic or hyperbolic).
What is the ecliptic plane?
The plane of Earth's orbit around the Sun
ecliptic plane
The plane of Earth's orbit around the Sun.
If we observe one edge of a planet to be redshifted and the opposite edge to be blueshifted, what can we conclude about the planet?
The planet is rotating.
Suppose we make a scale model of our solar system, with the Sun the size of a grapefruit. Which of the following best describes what the planets would look like?
The planets are all much smaller than the Sun. Four planets are within about 20 meters of the Sun, while the rest planets are spread much farther apart.
observable universe
The portion of the entire universe that can be seen from Earth, at least in principle. The observable universe is probably only a tiny portion of the entire universe.
observable universe
The portion of the entire universe that, at least in principle, can be seen from Earth.
nuclear fusion
The process in which two (or more) smaller nuclei slam together and make one larger nucleus.
Suppose you are listening to a radio station that broadcasts at a frequency of 97 Mhz (megahertz). Which of the following statements is true?
The radio waves from the radio station are causing electrons in your radio's antenna to move up and down 97 million times each second.
rotation
The spinning of an object around its axis.
Laboratory measurements show hydrogen produces a spectral line at a wavelength of 486.1 nanometers (nm). A particular star's spectrum shows the same hydrogen line at a wavelength of 486.0 nm. What can we conclude?
The star is moving toward us.
Which of the following best describes what we mean by the universe?
The sum total of all matter and energy
universe
The sum total of all matter and energy.
universe (or cosmos)
The sum total of all matter and energy—that is, all galaxies and everything between them.
All of the following statements about the Sun's corona are true. Which one explains why it is a source of X rays?
The temperature of the corona's gas is some 1 to 2 million Kelvin.
Which of the following is not a reason why telescopes tend to be built on mountaintops that are relatively far from cities and are in regions with dry climates?
The thin air on mountaintops makes the glass in telescope mirrors less susceptible to warping.
Studying a spectrum from a star can tell us a lot. All of the following statements are true except one. Which statement is not true?
The total amount of light in the spectrum tells us the star's radius.
The planet Neptune is blue in color. How would you expect the spectrum of visible light from Neptune to be different from the visible-light spectrum of the Sun?
The two spectra would have similar shapes, except Neptune's spectrum would be missing a big chunk of the red light that is present in the Sun's spectrum.
The fact that nearly all galaxies are moving away from us, with more distant ones moving faster, helped us to conclude that:
The universe is expanding
Which of the following is always true about images captured with X-ray telescopes?
They are always shown with colors that are not the true colors of the objects that were photographed.
Suppose you watch a leaf bobbing up and down as ripples pass it by in a pond. You notice that it does two full up and down bobs each second. Which statement is true of the ripples on the pond?
They have a frequency of 2 hertz.
Which of the following best describes the fundamental difference between two different chemical elements (such as oxygen and carbon)?
They have different numbers of protons in their nucleus.
The lens in your eye forms an upside-down image of the world.
True
milky way
Used both as the name of our galaxy and to refer to the band of light we see in the sky when we look into the plane of our galaxy.
higher in the sky
When traveling north from the United States into Canada, you'll see the North Star (Polaris) getting _________.
The "celestial sphere" is another name for our universe.
Which of the following statements about the celestial sphere is NOT true?
When did humans learn that the Earth is not the center of the universe?
Within the past 500 years
Why can't X-ray and gamma-ray telescopes use the same designs as visible-light telescopes?
X rays and gamma rays have so much energy that they cannot be reflected in the same way as visible light.
The Chandra X-ray Observatory must operate in space because:
X rays do not penetrate Earth's atmosphere.
Which of the following statements about X rays and radio waves is not true?
X rays travel through space faster than radio waves.
A full moon high in the sky
You observe a full Moon rising at sunset. What will you see at midnight?
Which of the following has your "cosmic address" in the correct order?
You, Earth, solar system, Milky Way Galaxy, Local Group, Local Supercluster, universe
Visible light from a distant star can be spread into a spectrum by using a glass prism or ______.
a diffraction grating
The number of stars in the Milky Way Galaxy is approximately _________.
a few hundred billion
No object produces a perfect thermal radiation spectrum, but many objects produce close approximations. Which of the following would not produce a close approximation to a thermal radiation spectrum?
a hot, thin (low-density, nearly transparent) gas
According to the laws of thermal radiation, hotter objects emit photons with _________.
a shorter average wavelength
What is the angular resolution of the human eye?
about 1 arcminute, or 1/60 of a degree
A light-year is _________.
about 10 trillion kilometers
If we say that a material is opaque to ultraviolet light, we mean that it _________.
absorbs ultraviolet light
Consider a raisin cake expanding uniformly in an oven. Viewed from one of the raisins, you would see _____.
all other raisins moving away from you, with more distant raisins moving faster
Astronomers infer that the universe is expanding because distant galaxies all appear to
be moving away from us, with more distant ones moving faster
Astronomers infer that the universe is expanding because distant galaxies all appear to _________.
be moving away from us, with more distant ones moving faster
A typical galaxy is a _________.
collection of a few hundred million to a trillion or more stars, bound together by gravity
The Earth rotates one a _ on its acis and orbits the Sun once each _ The eliptic plane is the plane defines by _ 's orbit around _. Axis tolt of a planet is the amount that _ is tipped relative to a line perpendicular to the ecliptic plane.
day, year, Earth, the Sun, its axis
From shortest to longest wavelength, which of the following correctly orders the different categories of electromagnetic radiation?
gamma rays, X rays, ultraviolet, visible light, infrared, radio
The spectra of most galaxies show redshifts. This means that their spectral lines _________.
have wavelengths that are longer than normal
Which forms of light are lower in energy and frequency than the light that our eyes can see?
infrared and radio
An atom that has fewer electrons than protons is called a/an _________.
ion
A television advertisement claiming that a product is light-years ahead of its time does not make sense because
it uses "light-years" to talk about time, but a light-year is a unit of distance
A television advertisement claiming that a product is light-years ahead of its time does not make sense because _________.
it uses "light-years" to talk about time, but a light-year is a unit of distance
Suppose you know the frequency of a photon and the speed of light. What else can you determine about the photon?
its wavelength and energy
If we imagine the history of the universe compressed into one year, dinosaurs became extinct
yesterday morning
If we imagine the history of the universe compressed into one year, dinosaurs became extinct _________.
yesterday morning