Lesson 10

Question 1

What do asteroids and comets have in common?

Answer 1

Most are unchanged since their formation in the solar nebula

Question 2

What is the size of the largest asteroid?

Answer 2

1000 km

Question 3

How does the largest asteroid, Ceres, compare in size to other solar system worlds?

Answer 3

It is about a quarter the size of the Moon

Question 4

Which is closest to the average distance between asteroids in the asteroid belt?

Answer 4

1 million km

Question 5

Where are the Trojan asteroids located?

Answer 5

Along Jupiter’s orbit, 60° ahead of and behind Jupiter

Question 6

We know that there are large gaps in the average distances of asteroids from the Sun (within the asteroid belt) because we

Answer 6

have plotted distributions of the orbital radii of the asteroids

Question 7

Why do we sometimes observe asteroids at the distances of the gaps in the asteroid belt?

Answer 7

A gap is located at an average orbital distance, and asteroid orbits often have large eccentricities

Question 8

How can we determine an asteroid’s reflectivity?

Answer 8

by comparing its infrared thermal emission to its visible-light reflection

Question 9

If we know the size of an asteroid, we can determine its density by

Answer 9

determining its mass from its gravitational pull on spacecraft, satellite, or planet.

Question 10

A typical shooting star in a meteor shower is caused by a ________ entering Earth’s atmosphere.

Answer 10

pea-size particle from a comet

Question 11

Processed meteorites with low metal content probably are

Answer 11

chunks of a larger asteroid that was shattered by a collision

Question 12

When do comets generally begin to form a tail?

Answer 12

inside of Jupiter’s orbit

Question 13

here did comets that are now in the Oort cloud originally form?

Answer 13

near the jovian planets

Question 14

Where did comets that are now in the Kuiper belt originally form?

Answer 14

near the radius at which they orbit today

Question 15

The number of comets in the Oort cloud is probably about

Answer 15

a trillion

Question 16

Why won’t Pluto collide with Neptune?

Answer 16

The two planets have an orbital resonance that prevents them from colliding

Question 17

In the asteroid impact theory of the extinction of the dinosaurs some 65 million years ago, the dinosaurs (and over half of all the other species on Earth at that time) died off largely because

Answer 17

dust injected into the stratosphere from the impact absorbed visible light from the Sun, causing global temperatures to plummet.

Question 18

Which of the following Pluto observations did not help convince scientists to change Pluto’s status from that of a planet?

Answer 18

discovery of Pluto’s 3 moons

Question 19

Which statement is not thought to be true of all comets in our solar system?

Answer 19

Comets always have tails

Question 20

What was the Shoemaker-Levy 9 impact?

Answer 20

the 1994 impact of a chain of comet fragments into Jupiter

Question 21

Suppose there were no solar wind. How would the appearance of a comet in our inner solar system be different?

Answer 21

It would have only one tail instead of two

Question 22

Suppose we discover a new comet on an orbit that brings it closer to the Sun than Mercury every 125 years. What can we conclude?

Answer 22

It has been on its current orbit for only a very short time compared to the age of our solar system

Question 23

Why won’t Pluto collide with Neptune?

Answer 23

Pluto orbits the Sun exactly 2 times for every 3 Neptune orbits, which ensures they never come close together

Question 24

Which of the following is not a piece of evidence supporting the idea that an impact caused the mass extinction that occurred 65 million years ago?

Answer 24

Fossilized dinosaur bones contain fragments of rock from the impact.