Question 1

Comets that we find in the Kuiper belt are believed to have formed:

Accepted Answer

A) in the inner solar system. Sunlight, and the solar wind acting over billions of years, have pushed them out past the orbit of Pluto. 
B) in elliptical orbits extending out to tens of thousands of astronomical units, and gravitational interactions with the giant planets have circularized their orbits into a band beyond Pluto. 
C) exactly where we see them now, in a band beyond the orbit of Pluto. 
D) between the orbits of Jupiter and Neptune. They were flung out beyond Pluto by gravitational interactions with the giant planets. 
A) in the inner solar system. Sunlight, and the solar wind acting over billions of years, have pushed them out past the orbit of Pluto. 
B) in elliptical orbits extending out to tens of thousands of astronomical units, and gravitational interactions with the giant planets have circularized their orbits into a band beyond Pluto. 
C) exactly where we see them now, in a band beyond the orbit of Pluto. 
D) between the orbits of Jupiter and Neptune. They were flung out beyond Pluto by gravitational interactions with the giant planets. C

Question 2

The orbits of asteroids have a surprisingly large variety of semimajor axes, eccentricities, and inclinations to the ecliptic compared to most of the major planets. Which of these seems to be a reasonable explanation for this?

Accepted Answer

A) Asteroids are "small" objects, and they formed with the kinds of orbits they now have. 
B) The orbits were stirred up when the Sun passed within the Oort cloud of another star. 
C) Jupiter's gravitational pull has stirred up the asteroid orbits. 
D) One or more Mars-sized planets formed in the asteroid belt, and their gravitational influence stirred up the orbits of the rest of the asteroids. 
A) Asteroids are "small" objects, and they formed with the kinds of orbits they now have. 
B) The orbits were stirred up when the Sun passed within the Oort cloud of another star. 
C) Jupiter's gravitational pull has stirred up the asteroid orbits. 
D) One or more Mars-sized planets formed in the asteroid belt, and their gravitational influence stirred up the orbits of the rest of the asteroids. C

Question 3

An iron meteorite, when cut open and etched with acid, often shows a peculiar pattern of nickel-iron crystals called a Widmanstätten pattern. Through what process was this pattern created?

Accepted Answer

A) partial melting during the impact that ejected the meteorite from its parent asteroid, with subsequent rapid cooling in space 
B) rapid crystal growth as molten iron cooled and solidified in the interior of a small asteroid 
C) slow crystal growth as iron condensed from gas directly to solid form in the early solar nebula 
D) slow crystal growth as molten iron cooled and solidified in the interior of a large asteroid 
A) partial melting during the impact that ejected the meteorite from its parent asteroid, with subsequent rapid cooling in space 
B) rapid crystal growth as molten iron cooled and solidified in the interior of a small asteroid 
C) slow crystal growth as iron condensed from gas directly to solid form in the early solar nebula 
D) slow crystal growth as molten iron cooled and solidified in the interior of a large asteroid D

Question 4

How do the biggest asteroids compare in size with the Moon?

Accepted Answer

A) They are very much smaller (less than 1/10). 
B) They are between 1/10 and 1/2 as large. 
C) They are about the same size. 
D) They are very much larger (greater than 5×). 
A) They are very much smaller (less than 1/10). 
B) They are between 1/10 and 1/2 as large. 
C) They are about the same size. 
D) They are very much larger (greater than 5×).

Question 5

A typical iron meteorite shows a Widmanstätten pattern. This suggests that it is a(n):

Accepted Answer

A) iron-nickel object that has existed unheated from the beginning of the solar system. 
B) fragment of an undifferentiated (primitive) asteroid. 
C) fragment from the core of a differentiated asteroid. 
D) fragment from the crust of a differentiated asteroid. 
A) iron-nickel object that has existed unheated from the beginning of the solar system. 
B) fragment of an undifferentiated (primitive) asteroid. 
C) fragment from the core of a differentiated asteroid. 
D) fragment from the crust of a differentiated asteroid.

Question 6

The huge hydrogen cloud that surrounds the nucleus of a comet has a typical diameter of about:

Accepted Answer

A) 1/2 au. 
B) 2 au. 
C) 1 million km. 
D) 10 million km. 
A) 1/2 au. 
B) 2 au. 
C) 1 million km. 
D) 10 million km.

Question 7

The Kirkwood gaps are found in the:

Accepted Answer

A) equatorial region of the Sun. 
B) rings of Saturn. 
C) spectrum of hydrogen gas. 
D) asteroid belt. 
A) equatorial region of the Sun. 
B) rings of Saturn. 
C) spectrum of hydrogen gas. 
D) asteroid belt.

Question 8

Which of the following descriptions would allow you tentatively to identify a rock as a fallen meteorite?

Accepted Answer

A) layered rock, consisting of limestone 
B) solid iron, with a distinctive crystal structure throughout its interior 
C) rough-surfaced rock with small inclusions of coal 
D) large transparent crystals of common salt embedded in sandstone 
A) layered rock, consisting of limestone 
B) solid iron, with a distinctive crystal structure throughout its interior 
C) rough-surfaced rock with small inclusions of coal 
D) large transparent crystals of common salt embedded in sandstone

Question 9

Iron meteorites:

Accepted Answer

A) are normally composed almost entirely of iron and nickel. 
B) are normally composed almost entirely of iron. 
C) normally contain between 3 and 5 times as much iron as terrestrial rocks, in the form of pure grains embedded a rocky matrix. 
D) are normally composed almost entirely of iron, nickel, and carbon. 
A) are normally composed almost entirely of iron and nickel. 
B) are normally composed almost entirely of iron. 
C) normally contain between 3 and 5 times as much iron as terrestrial rocks, in the form of pure grains embedded a rocky matrix. 
D) are normally composed almost entirely of iron, nickel, and carbon.

Question 10

If an impact crater on Earth is 2000 m wide, approximately how big would the asteroid fragment have been that survived its passage through the atmosphere?

Accepted Answer

A) 20 m 
B) 100 m 
C) 2000 m 
D) 4 km 
A) 20 m 
B) 100 m 
C) 2000 m 
D) 4 km

Question 11

What is the approximate orbital period of an object that is moving in a circular orbit around the Sun at the inner edge of the doughnut-shaped part of the Oort cloud?

Accepted Answer

A) 1000 years 
B) 100,000 years 
C) 10,000 years 
D) 10,000,000 years 
A) 1000 years 
B) 100,000 years 
C) 10,000 years 
D) 10,000,000 years

Question 12

A meteorite is seen to impact upon Earth and is found to contain significant amounts of 26Mg, the stable decay product of radioactive 26Al. What conclusion can be drawn from this observation?

Accepted Answer

A) Radioactivity occurs naturally in normal matter and so this finding is not surprising. 
B) An energetic nuclear event, possibly a supernova, occurred near the Sun and produced 26Al at about the time that this meteorite was formed. 
C) The meteorite became so hot on its descent through Earth's atmosphere, that it became radioactive. 
D) The meteorite had probably passed through radioactive clouds in space before hitting Earth. 
A) Radioactivity occurs naturally in normal matter and so this finding is not surprising. 
B) An energetic nuclear event, possibly a supernova, occurred near the Sun and produced 26Al at about the time that this meteorite was formed. 
C) The meteorite became so hot on its descent through Earth's atmosphere, that it became radioactive. 
D) The meteorite had probably passed through radioactive clouds in space before hitting Earth.

Question 13

Why do most comets have very elliptical orbits, often extending far out beyond the orbit of Pluto?

Accepted Answer

A) They originally formed in circular orbits far from the Sun (> 500 au), and passing stars have perturbed them into long, elliptical orbits. 
B) They are interstellar objects that have been captured in orbit by the Sun. 
C) They formed so far from the Sun (e.g., 10,000 au) that their orbits naturally drop deeply into the inner solar system. 
D) They originally formed outside the orbit of Pluto and were flung into highly elongated orbits by the giant planets. 
A) They originally formed in circular orbits far from the Sun (> 500 au), and passing stars have perturbed them into long, elliptical orbits. 
B) They are interstellar objects that have been captured in orbit by the Sun. 
C) They formed so far from the Sun (e.g., 10,000 au) that their orbits naturally drop deeply into the inner solar system. 
D) They originally formed outside the orbit of Pluto and were flung into highly elongated orbits by the giant planets.

Question 14

The number of times that a typical comet can pass close to the Sun (i.e., the number of orbits that the comet can complete) before it completely vaporizes is between:

Accepted Answer

A) 10,000 and 50,000. 
B) 1 and 5. 
C) 10 and 25. 
D) 100 and 200. 
A) 10,000 and 50,000. 
B) 1 and 5. 
C) 10 and 25. 
D) 100 and 200.

Question 15

An iron meteorite, when cut open and etched with acid, often shows a peculiar pattern of nickel-iron crystals called a Widmanstätten pattern. What does the presence of this pattern tell us about the meteorite?

Accepted Answer

A) It was blasted from the surface of the planet Mars by an impact. 
B) It is a fragment of a shattered asteroid that was at least 200 km in diameter. 
C) It is a primitive (unaltered) piece of the early solar nebula. 
D) It is a fragment of a shattered asteroid that was no more than about 25 km in diameter. 
A) It was blasted from the surface of the planet Mars by an impact. 
B) It is a fragment of a shattered asteroid that was at least 200 km in diameter. 
C) It is a primitive (unaltered) piece of the early solar nebula. 
D) It is a fragment of a shattered asteroid that was no more than about 25 km in diameter.

Question 16

One example of a near-Earth object, or NEO, is the:

Accepted Answer

A) DA 14 asteroid. 
B) Moon. 
C) asteroid Ceres. 
D) Trojan asteroid Hector. 
A) DA 14 asteroid. 
B) Moon. 
C) asteroid Ceres. 
D) Trojan asteroid Hector.

Question 17

What kind of orbits do the Trojan asteroids follow?

Accepted Answer

A) circular orbits at the same distance from the Sun as Jupiter 
B) circular orbits at about 2.8 au from the Sun 
C) long, elliptical orbits that cross that of Earth 
D) long, elliptical orbits ranging from Neptune's orbital distance to Jupiter's orbital distance 
A) circular orbits at the same distance from the Sun as Jupiter 
B) circular orbits at about 2.8 au from the Sun 
C) long, elliptical orbits that cross that of Earth 
D) long, elliptical orbits ranging from Neptune's orbital distance to Jupiter's orbital distance

Question 18

The most ambitious mission so far to study the asteroids is:

Accepted Answer

A) a flyby mission to take close-up images of an asteroid. 
B) a spacecraft that went into orbit around an asteroid. 
C) a soft robotic landing to gather materials and return them to Earth. 
D) a crewed landing to explore the asteroid and then return to Earth. 
A) a flyby mission to take close-up images of an asteroid. 
B) a spacecraft that went into orbit around an asteroid. 
C) a soft robotic landing to gather materials and return them to Earth. 
D) a crewed landing to explore the asteroid and then return to Earth.

Question 19

Comet tails are the result of:

Accepted Answer

A) sunlight glinting on and reflecting from the icy nucleus of a comet. 
B) dust collected by the comet as it moves in its orbit. 
C) solar wind particles being guided and excited to emit light by the comet's magnetic field. 
D) melting and evaporation of ices from the comet's nucleus. 
A) sunlight glinting on and reflecting from the icy nucleus of a comet. 
B) dust collected by the comet as it moves in its orbit. 
C) solar wind particles being guided and excited to emit light by the comet's magnetic field. 
D) melting and evaporation of ices from the comet's nucleus.

Question 20

Statistically, an asteroid 1 km in diameter might be expected to strike Earth:

Accepted Answer

A) during an interval of 80 years-roughly a human lifetime. 
B) once every 10,000 years. 
C) once every 500,000 years. 
D) never. 
A) during an interval of 80 years-roughly a human lifetime. 
B) once every 10,000 years. 
C) once every 500,000 years. 
D) never.

Exam 15: Asteroids, Comets, and Impacts

Comets that we find in the Kuiper belt are believed to have formed:

The orbits of asteroids have a surprisingly large variety of semimajor axes, eccentricities, and inclinations to the ecliptic compared to most of the major planets. Which of these seems to be a reasonable explanation for this?

An iron meteorite, when cut open and etched with acid, often shows a peculiar pattern of nickel-iron crystals called a Widmanstätten pattern. Through what process was this pattern created?

How do the biggest asteroids compare in size with the Moon?

A typical iron meteorite shows a Widmanstätten pattern. This suggests that it is a(n):

The huge hydrogen cloud that surrounds the nucleus of a comet has a typical diameter of about:

The Kirkwood gaps are found in the:

Which of the following descriptions would allow you tentatively to identify a rock as a fallen meteorite?

Iron meteorites:

If an impact crater on Earth is 2000 m wide, approximately how big would the asteroid fragment have been that survived its passage through the atmosphere?

What is the approximate orbital period of an object that is moving in a circular orbit around the Sun at the inner edge of the doughnut-shaped part of the Oort cloud?

A meteorite is seen to impact upon Earth and is found to contain significant amounts of 26Mg, the stable decay product of radioactive 26Al. What conclusion can be drawn from this observation?

Why do most comets have very elliptical orbits, often extending far out beyond the orbit of Pluto?

The number of times that a typical comet can pass close to the Sun (i.e., the number of orbits that the comet can complete) before it completely vaporizes is between:

An iron meteorite, when cut open and etched with acid, often shows a peculiar pattern of nickel-iron crystals called a Widmanstätten pattern. What does the presence of this pattern tell us about the meteorite?

One example of a near-Earth object, or NEO, is the:

What kind of orbits do the Trojan asteroids follow?

The most ambitious mission so far to study the asteroids is:

Comet tails are the result of:

Statistically, an asteroid 1 km in diameter might be expected to strike Earth:

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

Quasars and Active Galaxies

Cosmology: The Origin and Evolution of the Universe

Exploring the Early Universe

The Search for Extraterrestrial Life

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A meteorite is seen to impact upon Earth and is found to contain significant amounts of ²⁶Mg, the stable decay product of radioactive ²⁶Al. What conclusion can be drawn from this observation?