Question 1

The expected (and now measured, at least for Halley's Comet) size of the nucleus of a typical comet is about:

Accepted Answer

A) 106 km. 
B) 107 km. 
C) 10 km. 
D) 100 m. 
A) 106 km. 
B) 107 km. 
C) 10 km. 
D) 100 m.

Question 2

Most asteroids:

Accepted Answer

A) are dark and spherical in shape, with many craters on their surfaces. 
B) are spherical and ice coated, and hence light colored and shiny. 
C) are irregularly shaped and covered with very light-colored dust that reflects sunlight well. 
D) are dark, irregular in shape, and heavily cratered. 
A) are dark and spherical in shape, with many craters on their surfaces. 
B) are spherical and ice coated, and hence light colored and shiny. 
C) are irregularly shaped and covered with very light-colored dust that reflects sunlight well. 
D) are dark, irregular in shape, and heavily cratered.

Question 3

The Tunguska event of 1908 was probably caused by a stony body. Why was so little obvious evidence of meteoric impact found at the scene?

Accepted Answer

A) Evidence of a large impact like this one is highly radioactive. But during the two decades between the event and the investigation, the radioactivity had subsided. 
B) The stony contents were all incinerated high in the atmosphere. 
C) The stony contents all vaporized on impact, like those in the Barringer Crater in Arizona. 
D) The stony contents were distributed widely over the ground. But after a few years of weathering, they became indistinguishable from ordinary rocks. 
A) Evidence of a large impact like this one is highly radioactive. But during the two decades between the event and the investigation, the radioactivity had subsided. 
B) The stony contents were all incinerated high in the atmosphere. 
C) The stony contents all vaporized on impact, like those in the Barringer Crater in Arizona. 
D) The stony contents were distributed widely over the ground. But after a few years of weathering, they became indistinguishable from ordinary rocks.

Question 4

The Kirkwood gaps are primarily caused by:

Accepted Answer

A) the gravitational tug of Jupiter nudging asteroids into new orbits. 
B) shepherd satellites controlling the orbits of ring particles. 
C) orbits of material being disturbed because Jupiter's gravitational field balances the Sun at this distance, and objects can escape from the solar system. 
D) large asteroids sweeping parts of the asteroid belt clear of smaller asteroids. 
A) the gravitational tug of Jupiter nudging asteroids into new orbits. 
B) shepherd satellites controlling the orbits of ring particles. 
C) orbits of material being disturbed because Jupiter's gravitational field balances the Sun at this distance, and objects can escape from the solar system. 
D) large asteroids sweeping parts of the asteroid belt clear of smaller asteroids.

Question 5

Showers of shooting stars or meteors are seen at regular times each year on Earth because:

Accepted Answer

A) Earth passes through the fringes of the asteroid belt at these times. 
B) Earth is bombarded by material, including dust grains, ejected from the Sun during regular sunspot activity. 
C) Earth runs into material within the spiral arm structure of the Milky Way at these times. 
D) Earth passes through a cloud of remnant dust and rock fragments from an old comet that is circling the Sun in the comet's old orbit. 
A) Earth passes through the fringes of the asteroid belt at these times. 
B) Earth is bombarded by material, including dust grains, ejected from the Sun during regular sunspot activity. 
C) Earth runs into material within the spiral arm structure of the Milky Way at these times. 
D) Earth passes through a cloud of remnant dust and rock fragments from an old comet that is circling the Sun in the comet's old orbit.

Question 6

If objects in the asteroid belt are prevented from occupying an orbit for which their period would be one-third of that of Jupiter because of repeated gravitational disturbances, at what distance would you expect a gap in the asteroid belt?

Accepted Answer

A) 1.0 au 
B) 7.86 au 
C) 3.28 au 
D) 2.5 au 
A) 1.0 au 
B) 7.86 au 
C) 3.28 au 
D) 2.5 au

Question 7

Suppose an intense meteor shower occurs on a certain date this year, but there was no shower last year on that date, and it turns out that there is no shower next year on that date. A likely explanation is that:

Accepted Answer

A) this year Earth passed through the orbit of a recently disintegrated comet, one for which the debris is not yet distributed along the entire orbit. 
B) a small comet has passed through Earth's atmosphere. 
C) the meteor shower is the remnant of a comet that had a semimajor axis larger than 1 au and a period longer than 1 year. 
D) the debris along the orbit was mostly fine dust, which has been blown away by the solar wind. 
A) this year Earth passed through the orbit of a recently disintegrated comet, one for which the debris is not yet distributed along the entire orbit. 
B) a small comet has passed through Earth's atmosphere. 
C) the meteor shower is the remnant of a comet that had a semimajor axis larger than 1 au and a period longer than 1 year. 
D) the debris along the orbit was mostly fine dust, which has been blown away by the solar wind.

Question 8

What is the relationship between the Kirkwood gaps in the asteroid belt and the Cassini and Enke divisions in the rings of Saturn?

Accepted Answer

A) Both are caused by large objects passing through swarms of smaller objects, sweeping out gaps in the swarms. 
B) Both were discovered by observers from the same group; Kirkwood and Enke worked at the Cassini Observatory. 
C) Both are caused by selective melting of material at these specific locations from the central radiating body, the Sun and Saturn respectively. 
D) Both are caused by disruptions of orbits of small objects by a larger object whose orbital period is a simple ratio of that of the small objects. 
A) Both are caused by large objects passing through swarms of smaller objects, sweeping out gaps in the swarms. 
B) Both were discovered by observers from the same group; Kirkwood and Enke worked at the Cassini Observatory. 
C) Both are caused by selective melting of material at these specific locations from the central radiating body, the Sun and Saturn respectively. 
D) Both are caused by disruptions of orbits of small objects by a larger object whose orbital period is a simple ratio of that of the small objects.

Question 9

About 6% of the meteorites landing on Earth are thought to come from which asteroid?

Accepted Answer

A) Ceres 
B) Vesta 
C) Gaspra 
D) Mathilde 
A) Ceres 
B) Vesta 
C) Gaspra 
D) Mathilde

Question 10

What experimental technique was used to discover the huge hydrogen cloud that surrounds the nucleus and the coma of a comet?

Accepted Answer

A) Hubble Space Telescope IR photography 
B) ground-based photography, at the hydrogen Balmer $\alpha$ wavelength 
C) radio measurements at 21 cm wavelength 
D) rocketborne ultraviolet photography 
A) Hubble Space Telescope IR photography 
B) ground-based photography, at the hydrogen Balmer $\alpha$ wavelength 
C) radio measurements at 21 cm wavelength 
D) rocketborne ultraviolet photography

Question 11

A meteorite is a solid object reaching Earth's surface after plunging through our atmosphere. A meteorite might have originally been a part of any of the following EXCEPT:

Accepted Answer

A) a meteoroid or asteroid. 
B) a comet. 
C) the Van Allen radiation belt. 
D) Mars or the Moon. 
A) a meteoroid or asteroid. 
B) a comet. 
C) the Van Allen radiation belt. 
D) Mars or the Moon.

Question 12

Asteroids should be able to remain stably trapped at the stable Lagrange points of the Earth-Sun system (See Figure 15-14 of Universe, 11th ed.), provided they are NOT subjected to other, stronger, gravitational influences. As a test of this stability, calculate how strong Jupiter's gravity is on a mass at Earth's stable Lagrange points (when Jupiter is closest to them) compared to the strength of Earth's gravity on the same mass at the same points. (You will need to use Newton's law of gravitation; it will also help to draw a diagram.) Compared to Earth's gravitational force at these points, Jupiter's gravity is:
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Accepted Answer

A) 1/18 as strong. 
B) 18 times stronger. 
C) 12 times stronger. 
D) 76 times stronger. 
A) 1/18 as strong. 
B) 18 times stronger. 
C) 12 times stronger. 
D) 76 times stronger.

Question 13

The Deep Impact mission to Comet Tempel 1 measured the density of the comet's nucleus. This was found to be:

Accepted Answer

A) about the density of iron. 
B) about the density of ordinary rock. 
C) less than the density of water. 
D) so small as to suggest that the nucleus is hollow. 
A) about the density of iron. 
B) about the density of ordinary rock. 
C) less than the density of water. 
D) so small as to suggest that the nucleus is hollow.

Question 14

The object found about 2.8 au from the Sun when astronomers were looking for a "missing" planet between the orbital distances of Mars and Jupiter was:

Accepted Answer

A) the asteroid Ceres. 
B) Pluto. 
C) Halley's Comet. 
D) Mercury. 
A) the asteroid Ceres. 
B) Pluto. 
C) Halley's Comet. 
D) Mercury.

Question 15

The Trojan asteroids orbit the Sun in circular orbits at the same distance as:

Accepted Answer

A) the main asteroid belt. 
B) Jupiter. 
C) Mars. 
D) Earth. 
A) the main asteroid belt. 
B) Jupiter. 
C) Mars. 
D) Earth.

Question 16

The hydrogen envelope of a bright comet is:

Accepted Answer

A) visible to the naked eye from Earth's surface. 
B) not visible from Earth's surface because of atmospheric absorption, but it is visible to the naked eye from a spacecraft above the atmosphere. 
C) created from water molecules that are broken apart by infrared radiation from the Sun. 
D) visible in an ultraviolet telescope above Earth's atmosphere. 
A) visible to the naked eye from Earth's surface. 
B) not visible from Earth's surface because of atmospheric absorption, but it is visible to the naked eye from a spacecraft above the atmosphere. 
C) created from water molecules that are broken apart by infrared radiation from the Sun. 
D) visible in an ultraviolet telescope above Earth's atmosphere.

Question 17

The description of a comet as a "dirty snowball" applies to the:

Accepted Answer

A) nucleus. 
B) coma. 
C) envelope. 
D) tail. 
A) nucleus. 
B) coma. 
C) envelope. 
D) tail.

Question 18

What is unusual about the asteroid Mathilde, which was studied and photographed by the NEAR spacecraft (See Figure 15-7 of Universe, 11th ed.)?
​
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Accepted Answer

A) It has almost no craters visible anywhere on its surface. 
B) It has a much higher mass for its volume than any other known asteroid. 
C) It is not much denser than water. 
D) It has a very bright surface, possibly caused by fresh material thrown out by impacts. 
A) It has almost no craters visible anywhere on its surface. 
B) It has a much higher mass for its volume than any other known asteroid. 
C) It is not much denser than water. 
D) It has a very bright surface, possibly caused by fresh material thrown out by impacts.

Question 19

The name 1987 FD refers to the:

Accepted Answer

A) fourth asteroid to be discovered in the month of February 1987. 
B) sixth asteroid to be discovered in the month of April 1987. 
C) 1987th asteroid ever to be discovered, named after Frances Draibre. 
D) fourth asteroid to be discovered during the second half of March 1987. 
A) fourth asteroid to be discovered in the month of February 1987. 
B) sixth asteroid to be discovered in the month of April 1987. 
C) 1987th asteroid ever to be discovered, named after Frances Draibre. 
D) fourth asteroid to be discovered during the second half of March 1987.

Question 20

Asteroids whose elliptical orbits have perihelion distances shorter than the orbital distance of Mars are known as:

Accepted Answer

A) Kirkwood objects, or KOs. 
B) near-Earth objects, or NEOs. 
C) Hirayama family asteroids, or HFAs. 
D) Mars-crossing asteroids, or MCAs. 
A) Kirkwood objects, or KOs. 
B) near-Earth objects, or NEOs. 
C) Hirayama family asteroids, or HFAs. 
D) Mars-crossing asteroids, or MCAs.

Exam 15: Asteroids, Comets, and Impacts

The expected (and now measured, at least for Halley's Comet) size of the nucleus of a typical comet is about:

Most asteroids:

The Tunguska event of 1908 was probably caused by a stony body. Why was so little obvious evidence of meteoric impact found at the scene?

The Kirkwood gaps are primarily caused by:

Showers of shooting stars or meteors are seen at regular times each year on Earth because:

If objects in the asteroid belt are prevented from occupying an orbit for which their period would be one-third of that of Jupiter because of repeated gravitational disturbances, at what distance would you expect a gap in the asteroid belt?

Suppose an intense meteor shower occurs on a certain date this year, but there was no shower last year on that date, and it turns out that there is no shower next year on that date. A likely explanation is that:

What is the relationship between the Kirkwood gaps in the asteroid belt and the Cassini and Enke divisions in the rings of Saturn?

About 6% of the meteorites landing on Earth are thought to come from which asteroid?

What experimental technique was used to discover the huge hydrogen cloud that surrounds the nucleus and the coma of a comet?

A meteorite is a solid object reaching Earth's surface after plunging through our atmosphere. A meteorite might have originally been a part of any of the following EXCEPT:

The Deep Impact mission to Comet Tempel 1 measured the density of the comet's nucleus. This was found to be:

The object found about 2.8 au from the Sun when astronomers were looking for a "missing" planet between the orbital distances of Mars and Jupiter was:

The Trojan asteroids orbit the Sun in circular orbits at the same distance as:

The hydrogen envelope of a bright comet is:

The description of a comet as a "dirty snowball" applies to the:

What is unusual about the asteroid Mathilde, which was studied and photographed by the NEAR spacecraft (See Figure 15-7 of Universe, 11th ed.)? ​ ​

The name 1987 FD refers to the:

Asteroids whose elliptical orbits have perihelion distances shorter than the orbital distance of Mars are known as:

Astronomy and the Universe

Knowing the Heavens

Eclipses and the Motion of the Moon

Gravitation and the Waltz of the Planets

The Nature of Light

Optics and Telescopes

Comparative Planetology I: Our Solar System

Comparative Planetology II: the Origin of Our Solar System

The Living Earth

Our Barren Moon

Mercury, Venus, and Mars: Terrestrial, yet Unique

Jupiter and Saturn: Lords of the Planets

Jupiter and Saturns Satellites of Fire and Ice

Uranus, Neptune, Pluto, and the Kuiper Belt: Remote Worlds

Our Star, the Sun

The Nature of the Stars

The Birth of Stars

Stellar Evolution: on and After the Main Sequence

Stellar Evolution: The Death of Stars

Stellar Remnants: Neutron Stars and Black Holes

Our Galaxy

Galaxies

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Cosmology: The Origin and Evolution of the Universe

Exploring the Early Universe

The Search for Extraterrestrial Life

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What is unusual about the asteroid Mathilde, which was studied and photographed by the NEAR spacecraft (See Figure 15-7 of Universe, 11th ed.)?