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AST FINAL YEEW!
Terms in this set (59)
When is the best time to view Saturn's rings?
when Saturn is in opposition, in the opposite side of the sky as the Sun
Which of the following is NOT a likely size (diameter) of the particles that comprise Saturn's rings?
What is the significance of the Roche Limit for a planet?
It is the minimum distance at which a moon can orbit a planet without being torn apart.
Most of Saturn's rings lie inside of Saturn's Roche Limit.
Tidal forces will destroy a satellite outside of a planet's Roche Limit.
Although the Voyager and Cassini spacecraft did not collect any samples of Saturn's ring particles, measurements from these spacecraft allowed scientists to determine the sizes of the particles. How was this done?
The trajectories of these spacecraft took them behind the rings so that the radio signal to Earth passed through the rings. The degree to which the signal was scattered indicated the particle size.
What is the structure of Saturn's rings?
Saturn's rings are composed of thousands of ringlets that are organized into the major rings.
What evidence is there that ring particles do not migrate significantly between ringlets?
The ring particles are not all the same color. Different colors are caused by chemicals, and they tend to segregate with different colors in different ringlets. These colors have remained constant, suggesting that particles do not migrate significantly between ringlets
How do shepherd satellites operate?
Shepherd satellites operate in pairs to keep ring particles confined to a narrow ring. The outer satellite slows the particles causing them to migrate inward. Then the inner satellite speeds them up again causing them to return to their original orbital distance.
Galileo Galilei, an Italian scientist, was the first person known to use a telescope to study the sky.
Jupiter's moons were known to the ancient Greeks, but they did not know what they were.
Io orbits faster than any of the other moons - it takes less than 2 days for Io to make a complete orbit.
Put the four Galilean moons in order of increasing speed of their orbits around Jupiter
Callisto, Ganymede, Europa, Io
When Galileo first saw the moons of Jupiter, what did he think they were
Which of the following was an important effect that Galileo's observations of the moons of Jupiter had on astronomy
His observation that the moons orbited Jupiter helped convince astronomers that Copernicus's Sun-centered model made better predictions than Earth-centered models
All of the Galilean satellites orbit Jupiter in the same direction. Furthermore, the planes of their orbits all lie within 0.5° of Jupiter's equatorial plane. What does this tell you about the idea that the Galilean satellites formed from a "Jovian nebula
A "Jovian nebula" would have flattened into an equatorial plane because of rotation before the Galilean satellites formed, just as the solar nebula did. Thus, this observation provides strong support for this hypothesis.
Io has no impact craters on its surface, whereas our Moon is covered with craters. Why are they different?
Tidal forces from Jupiter make Io very active geologically, and its surface is constantly reformed by volcanic output. This would erase any craters.
What aspects of Europa lead scientists to speculate that life may exist there?
Europa may have oceans of liquid water under its surface.
What precautions have been taken to prevent contaminating Europa with Earth organisms?
The Galileo spacecraft was sent to a fiery death in the Jovian atmosphere to avoid contaminating the surface of Europa with Earth organisms.
The Huygens probe fell through Titan's atmosphere and landed on its surface.
What substance flows through the rivers on Titan's surface?
Why was the discovery of hydrocarbon lakes near Titan's north pole so significant?
It was the first time that liquids were found on the surface of a Solar System body other than Earth
Could astronomers in antiquity have seen Uranus? If so, why was it not recognized as a planet?
Uranus at opposition is just barely visible to the naked eye and was undoubtedly seen by the ancients. But it moves very slowly, about four degrees per year, so that its motion is not readily apparent. With no special reason to watch this particular "dim star" over the course of several months, none of the ancient records identify it as a planet.
Uranus and Neptune appear bluish due to the large concentrations of water in their atmosphere.
Uranus and Neptune share the same temperature because
Neptune has an internal energy source while Uranus doesn't
What is unique about Uranus' rotation?
Uranus is the only planet tipped over on its side, with a tilt of over 90°
How does the energy source for Uranus's atmospheric motions compare with those on Jupiter, Saturn, and Neptune?
Jupiter, Saturn, and Neptune are still contracting and giving out energy. Some of this energy powers motions in their atmospheres. Uranus appears to have little or no internal source of heat, and uses only sunlight to power motions in its atmosphere.
y are Uranus and Neptune distinctly blue-green in color, whereas Jupiter and Saturn are not?
The atmospheres of both Uranus and Neptune contain substantial amounts of methane, whereas the atmospheres of Jupiter and Saturn do not. Methane absorbs the long wavelength part of the Sun's visible spectrum, allowing the blue and green to pass through.
Discuss the main reason why Uranus and Neptune are substantially smaller than Jupiter and Saturn.
Uranus and Neptune formed at a location closer to the Sun and were then moved to their present hydrogen- and helium-deficient region before they could accumulate much hydrogen and helium.
Which of the following are part of our evidence that Triton was captured by Neptune?
Triton's surface is relatively young.
Triton has a large orbital inclination.
Triton has a retrograde orbit.
It is thought that Pluto's tenuous atmosphere may become even thinner as the planet moves toward aphelion (which it will reach in 2113) and then regain its present density as it again moves toward perihelion. Why should this happen?
As Pluto approaches aphelion, the temperature drops and the atmosphere freezes out. As it approaches perihelion, the temperature rises and some of the ices evaporate
In order for a solar system object to be considered a planet, it must have a moon.
There are moons in our solar system which are bigger than Pluto.
Pluto's orbit is elliptical enough that for roughly 20 years every orbit, it passes closer to the Sun than Neptune.
Charon is the largest moon in comparison to its planet.
How was Pluto discovered?
Astronomers were looking for a much more massive object and they accidentally found Pluto.
Pluto's composition is most like
If you were standing on Pluto, how often would you see the satellite Charon rise above your horizon each day
Never - Charon is a synchronous satellite with an orbital period exactly equal to Pluto's rotation period
Currently how many discovered moons does Pluto have?
Suppose you wanted to search for trans-Neptunian objects. Why might it be advantageous to do your observations at infrared rather than visible wavelengths?
The average surface temperature of Pluto is 50 K. Wien's Law gives as the peak wavelength in its emitted spectrum about 58,000 nm, a wavelength well into the infrared.
The Kuiper belt has a surprisingly sharp outer edge; few Kuiper belt objects are found inside the orbit of Pluto. Why?
Objects at this radius are in gravitatioinal resonance with Neptune and are pulled inward.
What is a plutino?
any object that completes two revolutions of the Sun in the time it takes Neptune to complete three
The Kuiper belt extends from 30 AU (near the orbit of Neptune) outward to
If Jupiter had not formed, how would that have affected the asteroid belt?
If Jupiter had never formed, the asteroid belt might not exist. Without the effects of Jupiter's gravity, an Earth-sized planet might form in the asteroid belt. Jupiter's strong pull "clears out" the asteroid belt by disrupting the orbits of planetesimals in the belt, ejecting most of them from the solar system altogether.
What are the Kirkwood gaps, and what causes them?
The Kirkwood gaps are spaces in the asteroid belt where orbital resonance with Jupiter has removed asteroids.
The accompanying image from the Galileo spacecraft shows the asteroid 243I da, which has dimensions 56 × 24 × 21 km. Galileo discovered a tiny moon called Dactyl, just 1.6 × 1.4 × 1.2 km in size, which orbits Ida at a distance of about 100 km. (In Greek mythology, the Dactyli were beings who lived on the slopes of Mount Ida.) How might Ida have come to possess a moon?
Early in the history of the solar system, a collision between two large bodies might have produced a swarm of asteroids, including Ida and Dactyl.
One explanation for the existence of Dactyl is that Ida suffered a collision-ejection event with another asteroid that created Dactyl and placed it in orbit around Ida. This event would be a smaller version of the collision-ejection impact that created the Moon.
How is it possible to tell that some asteroids are non-spherical even though we do not have images of those asteroids?
An asteroid's shape can be determined by analyzing the reflections of a beam of radio waves sent to it from Earth.
What is the evidence that some asteroids are made of a loose conglomeration of smaller particles?
Some asteroids show large impact craters. Such an impact would have shattered a solid asteroid. But an asteroid that is a loose conglomeration held together by gravity would be able to absorb such an impact. The asteroid might come apart and then be pulled back together again.
A meteoroid is the term used to describe the meteor fragment that survives its passage through the Earth's atmosphere.
Carbonaceous chondrite meteorites likely contain primordial material.
The most common type of meteorite is which of the following?
Widmanstatten pattern indicates which of the following?
The meteorite was at least partially molten at one time.
Iron meteoroids tend to be homogeneous in composition because of which of the following?
They are pieces of an asteroid that differentiated before it broke up.
Is the phrase "dirty snowball" an appropriate characterization of a comet's nucleus?
Yes. A comet's nucleus is believed to be composed of ices plus some dirt, dust, and other solid particles.
Why are asteroids, meteoroids, and comets all of special interest to astronomers who want to understand the early history and subsequent evolution of the solar system?
Asteroids, meteorites, and comets are of special interest to astronomers who want to understand the early history of the solar system because these bodies have undergone fewer changes over billions of years compared with planets and satellites. This unchanged matter still contains information about the early solar system.
Where are the majority of the asteroids, or minor planets, found in the solar system?
in a broad region between the orbits of Mars and Jupiter
Which one of the following statements about asteroids is false?
Asteroids are a significant hazard to spacecraft passing through the asteroid belt.
In general, how do the asteroids compare with the trans-Neptunian objects?
The trans-Neptunian objects are larger and have more ice and less rock.
One surprising result of recent observations of asteroids by radar and by spacecraft exploration is that most asteroids of greater than about 1 km in diameter consist of
a loose collection of smaller, interplanetary "rubble."
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