astronomy test 2

infared telescope?

high altitude cold temperture

Would you expect as many impact craters per unit area on the surface of Venus as on the surface of Mars? Why or why not?

Because of its dense atmosphere, Venus is protected from smaller cratering impacts. Mars (with only a thin atmosphere) has thousands of craters smaller than this.

Earth contains radioactive elements whose decay produces neutrinos. How might we use neutrinos to determinehow these elements are distributed in Earth's interior?

By detecting the direction from which the neutrinos arrive at detectors in different locations, we can triangulate the location of potential sources within Earth. Note to instructors: Such detection of anti-neutrinos from decay processes within Earth is actually being done by the Kamioka Liquid Scintillator Antineutrino Detector.

Compare the eye, photographic film, and CCDs as detectors for light. What are the advantages and disadvantages of each?

Eye - Easy and cheap; imperfect because we process w/ our imperfect brain, Film - Photographic plate that makes a permanent record; only about 1% of the light contributes CCDs - light can be collected over longer periods of time similar

how are venus and earth geologically different?

lack of tectonic activity and high surface temperture

We believe that Venus, Earth, and Mars all started with a significant supply of water. Explain where that water is now for each planet.

mars has small gravity lost its atmosphere so water froze or evaporated. Venus heated up and turned it to vapor.

planet with similar seasons

mars, saturn, neptune

planet without seasonal activity

mercury

find free oxygen in giant planets?

no

extreme seasons?

pluto

Why have we found so many objects in the Kuiper belt in the last two decades and not before then?

really small needed new technology

Why do you suppose the rings of Saturn are made of bright particles, whereas the particles in the rings of Uranus and Neptune are black?

rings of Saturn were formed from the breakup of a parent body that was nearly pure water ice, while the rings of Uranus and Neptune are made of the dark organic material

three basic components of modern astronomical equipment

telescope, sorting instrument, and detector

Why are the largest visible-light telescopes in the world made with mirrors rather than lenses?

the use of a small secondary mirror allows more light to get through the system and to see the image clearer

why use radar imaging for venus

we have to penetrate its cloud cover

Why do astronomers place telescopes in Earth's orbit? What are the advantages for the different regions of the spectrum?

A. Getting above the distorting effects of the atmosphere is also an advantage at visible and Infrared wavelengths.To bypass earths disadvantages like clouds, storms and moisture having an telescope in space eliminates all of earths distractions.

What is the difference between a differentiated body and an undifferentiated body, and how might that influence a body's ability to retain heat for the age of the solar system?

A differentiated body is one that has been heated to the point where it is liquid, materials sink to the center lighter elements rise to the outer. The concentration of materials helps to retain heat in the interior of a planet. Undifferentiated bodies were never heated enough for the elements to separate; they cool quickly

Which type of object would likely cause more damage if it struck near an urban area: a small metallic object ora large stony/icy one?

A large (say, 50 m in diameter) stony or icy object would most likely explode and dissipate its energy in the atmosphere, with damage spread over a very large area beneath the impact zone. The smaller metallic object (say 2 m in diameter) would continue on to impact the surface and excavate a crater in the process. The extent of the crater would be much less than the extent of the atmospheric detonation; the latter would cause more damage over a wider area. However, either scenario would be rather unpleasant for the inhabitants of any nearby city.

Explain why the planet Venus is differentiated, but asteroid Fraknoi, a very boring and small member of theasteroid belt, is not.

A planet differentiates when its interior temperature rises above the melting point of the material it is made up of. A small asteroid such as Fraknoi, in contrast, loses its energy quickly and retains a cold interior.

Suppose you live in northern Canada and an extremely strong flare is reported on the Sun. What precautions might you take? What might be a positive result?

A strong flare may signal the ejection of charged particles from the Sun that can interfere with the operation of power stations and even cause the temporary loss of power on Earth. It might be appropriate to stock some candles, some wood for the fireplace, and some batteries to run devices so you can get information about when power might be restored. Since aurorae are often caused by these same charged particles, you might be treated to a fine display of the northern lights.

What is a charge-coupled device (CCD), and how is it used in astronomy?

A. A CCD is a modern detector similar to the detectors used in video camcordersB. High Pixels cameras, record brightness and color of image and computers sort info to create photo

When astronomers discuss the apertures of their telescopes, they say bigger is better. Explain why.

A. A bigger aperture allows you to use more magnification, higher resolution. Also collects light

Why is it difficult to observe at infrared wavelengths? What do astronomers do to address this difficulty?

A. It is difficult to distinguish between the amount of heat radiation that reaches Earth and the greater heat radiated by the telescope itself. B. To solve cooling and also by storing the detector in space or mountains

List the largest-aperture single telescope currently in use in each of the following bands of the electromagnetic spectrum: radio, X-ray, gamma ray.

A. Radio - 305-m , Arecibo, Puerto Rico B. X-ray - Chandra , earths satellite in space C. Gamma Ray - FERMI, in space

What is meant by "reflecting" and "refracting" telescopes?

A. Reflecting Telescopes use a mirror rather than a lens to form an imageB. Refracting Telescopes a long tube with a large glass lens at one end, uses a lens as its main optical element to form an image

Name the two spectral windows through which electromagnetic radiation easily reaches the surface of Earth and describe the largest-aperture telescope currently in use for each window.

A. Visible Light, Radio Waves B. Radio - 305-m , at Arecibo, Puerto Rico ; Visible Light - 10.4m Mirror, Canary Island

Compare the properties of the volcanoes on Io with those of terrestrial volcanoes. Give at least two similarities and two differences.

Although there are many differences in their style of eruption, the Io volcanoes are fundamentally like those of Earth, However, the heat to power the volcanoes on Io comes from tidal energy, whereas terrestrial volcanoes derive their power from radioactive heating of the mantle.

Present theory suggests that giant planets cannot form without condensation of water ice, which becomes vapor at the high temperatures close to a star. So how can we explain the presence of jovian-sized exoplanets closer to their star than Mercury is to our Sun?

Astronomers now believe that large planets may form far from their star, where low temperatures allow for condensation of ice, and then migrate inward closer to the star.

ch.7 Venus rotates backward and Uranus and Pluto spin about an axis tipped nearly on its side. Based on what you learned about the motion of small bodies in the solar system and the surfaces of the planets, what might be the cause of these strange rotations?

Collisions were frequent in the early solar system, so it is not unlikely that these strange rotations are due to collisions of these planets with significantly large objects during their formation or subsequent evolution.

Why is it unlikely that humans will be traveling to Io? (Hint: Review the information about Jupiter's magnetosphere in the chapter on The Giant Planets.)

Io is a long way from Earth; in terms of rocket energy and travel time, it is much harder to reach than Mars or Venus. The biggest problem, however, is the strong blast of rapidly moving charged particles (mostly ions of sulfur and oxygen) that are trapped in the jovian Van Allen belts and constantly bombard the surface of Io. For a human on the surface of Io or in orbit around it, this blast of subatomic particles would prove fatal in just a few minutes.

Why is it hard to give exact diameters for even the larger objects in the Kuiper belt?

Since objects in the Kuiper belt are too far away to resolve their diameters directly

Starting from the core of the Sun and going outward, the temperature decreases. Yet, above the photosphere, the temperature increases. How can this be?

Temperature is related to the average kinetic energy of the material. The magnetic fields that erupt into the chromosphere and corona dump energy into the particles there. Since it's not as dense, the particles in the chromosphere and corona can get to high velocities and so have high temperatures.

w do we know when the solar system formed? Usually we say that the solar system is 4.5 billion years old. To what does this age correspond?

The "age of the solar system" is defined to be the same as the age of its oldest members, which are the primitive meteorites. We use the radioactive materials in such meteorites to date them.

The Hooker telescope at Palomar Observatory has a diameter of 5 m, and the Keck I telescope has a diameter of 10 m. How much more light can the Keck telescope collect than the Hooker telescope in the same amount of time?

The Keck telescope can collect 4 times than the Hooker Telescope.

someone suggests that astronomers build a special gamma-ray detector to detect gamma rays produced duringthe proton-proton chain in the core of the Sun, just like they built a neutrino detector. Explain why this would be afruitless effort.

The gamma rays produced in the proton-proton chain are quickly absorbed by surrounding atoms in the Sun and reemitted with slightly less energy. This process occurs so many times that by the time the photons are released from the Sun, their energy has dropped from gamma-ray level to visible-light or UV-photon level. Thus, it is extremely unlikely that any gamma rays from the core of the Sun would be detected.

What does a planet need in order to retain an atmosphere? How does an atmosphere affect the surface of a planet and the ability of life to exist?

The gravity of a planet helps to determine whether an atmosphere can be retained. A dense atmosphere insulates the surface of a planet so that more heat is retained; however, the composition of the atmosphere is also important. Certain gases lead to a greenhouse effect

How can the prominences, which are so big and 'float' in the corona, stay gravitationally attached to the Sun while flares can escape?

The material has to achieve or exceed escape velocity from the Sun. Energetic flares can reach high enough speeds to escape (about 600 km/s), but the prominences do not.

Suppose the proton-proton cycle in the Sun were to slow down suddenly and generate energy at only 95% of itscurrent rate. Would an observer on Earth see an immediate decrease in the Sun's brightness? Would she immediatelysee a decrease in the number of neutrinos emitted by the Sun?

The observer would see a decrease in the number of neutrinos almost immediately since neutrinos take only about 2 seconds to travel from the center of the Sun to its surface and another 8 minutes to reach Earth. Light, on the other hand, takes about 105 to 106 years to traverse the distance from the center of the Sun to its surface, so 105 to 106 years would elapse before an observer on Earth saw a decrease in the brightness of the Sun.

Suppose you miraculously removed all of Saturn's moons. What would happen to its rings?

The rings would gradually expand (grow larger) in the plane they now occupy if the gravity of the inner moons were not present to confine their orbits.

If you were concerned about space weather and wanted to avoid it, where would be the safest place on Earth for you to live? Answer

The safest place to live on Earth would be on the equator in a valley. Earth's magnetic field deflects the charged particles ejected by the Sun onto the magnetic poles of Earth. Those are currently located in high and low (extreme northern and southern) latitudes, so the equator would be the safest place. Earth's atmosphere absorbs at least some of the energy, so a lower elevation would also be safer.

Which type of planets have the most moons? Where did these moons likely originate?

giant planets

uld you expect to find more impact craters on Io or Callisto? Why?

There are many more impact craters on Callisto because the impact craters on Io are removed (perhaps covered over) relatively rapidly by surface deposits from volcanic activity.

Earth's atmosphere is in hydrostatic equilibrium. What this means is that the pressure at any point in theatmosphere must be high enough to support the weight of air above it. How would you expect the pressure on Mt.Everest to differ from the pressure in your classroom? Explain why.

There is less air between the top of Mt. Everest and the outer edge of Earth's atmosphere than there is, say, between a location at sea level and the outer edge of the atmosphere. It takes less pressure to hold up the smaller mass above Mt. Everest. Since the altitude of your classroom is lower than that of Mt. Everest, the pressure in your classroom is higher. The summit of Mt. Everest is above about 70% of the molecules in Earth's atmosphere, and the pressure at the summit is only about 30% the pressure at sea level.

Suppose a comet were discovered approaching the Sun, one whose orbit would cause it to collide with Earth 20 months later, after perihelion passage. (This is approximately the situation described in the science-fiction novel Lucifer's Hammer by Larry Niven and Jerry Pournelle.) What could we do? Would there be any way to protect ourselves from a catastrophe?

This is an open-ended question. Blowing up the comet (say with a nuclear warhead) would not be a good solution, as this would merely produce many fragments that would likely do more damage in the end. We would need to produce an explosion that would divert the comet out of the path of Earth's orbit. Calculations show this would be possible with a large nuclear bomb if it were aimed properly, but today, such defensive action in so short a time is beyond our capability. We may never be able to deflect a comet discovered just a few months before its collision with Earth. In contrast, however, it would be relatively easy to change the orbit of an asteroid if we had several decades advanced warning that it would eventually collide with Earth. If students saw (or you have a chance to show) the 1997 film Deep Impact, you might want to comment on the realism (or lack of realism) of the comet deflection mission illustrated there.

Explain what it means when we say that Earth's oceans are in hydrostatic equilibrium. Now suppose you are ascuba diver. Would you expect the pressure to increase or decrease as you dive below the surface to a depth of 200feet? Why?

Water molecules have weight because they are attracted toward the solid surface of Earth by gravity. To keep the ocean from collapsing, there must be a force that acts to resist Earth's gravitational attraction. That force is pressure.

Why is fission not an important energy source in the Sun?

We know from our study of the Sun's spectrum that n the Sun that it would not be possible to generate a significant amount of energy by fission of these rare elements. m

Why would a flare be observed in visible light, when they are so much brighter in X-ray and ultraviolet light?

X-ray and ultraviolet light are absorbed by Earth's atmosphere, so those telescopes have to be in space and are relatively expensive. Less expensive visible-light telescopes can be used to observe the Sun since it's so close and the flares are still bright in visible light.

Why is there so much more carbon dioxide in the atmosphere of Venus than in that of Earth? Why so much more carbon dioxide than on Mars?

earth absorbs it into the ocean. escape velocity is smaller on mars so it escapes.

Why do iron meteorites represent a much higher percentage of finds than of falls?

easier to find

Why do you think the outer planets have such extensive systems of rings and moons, while the inner planets do not?

further from sun, can collect more debris