Chapter 13

In 2013, a small stony asteroid collided with the Earth above the Russian city of Chelyabinsk. What was the result?

A fireball briefly brighter than the Sun could be seen in the sky

The first asteroid to be discovered (which is also the largest one) is called

Ceres

When the Dawn spacecraft explored the largest asteroid Ceres, it discovered white spots that appear to be salt and volcanic mountains made of water ice. This led astronomers to which of the following ideas:

Ceres may have (or may have had) a liquid ocean under its crust

The scientist who first proposed that comet nuclei were "dirty snowballs" was:

Fred Whipple

The spacecraft that got the closest to the nucleus of Halley's Comet and sent back dramatic photographs of what the nucleus looked like was:

Giotto

The first asteroid confirmed to have a satellite (moon) was

Ida

The two asteroids from which close-up images and data have been returned by the Galileo spacecraft are:

Ida and Gaspra

According to our textbook, what is the best way to defend ourselves against an asteroid which is on course to collide with the Earth in 7 years?

If we do it early enough, we could explode something on or near the asteroid to deflect it slightly, so that years later it would then miss the Earth

Why do astronomers today think that we have an asteroid belt and not a planet between Mars and Jupiter?

Jupiter's gravity prevented material in that zone from getting together

Between 1992 and today, astronomers using large telescopes have discovered many icy pieces that orbit in the same region as the orbit of Pluto. These are believed to be members of the

Kuiper belt

In the far future, an entrepreneur with a large fleet of space ships decides to capture and bring to Earth some valuable asteroids. If at that time, there is a shortage of usable metals on Earth, what type of asteroids should his employees search for?

M-type

The Shoemaker-NEAR spacecraft explored two asteroids, Mathilde and Eros. A big difference between them is that:

Mathilde appears to be pile of "rubble" (a collection of separate rocks) while Eros is solid

Which of the following statements about NEO's (Near Earth Objects) is TRUE?

NEO's can include both asteroids and comets that cross the Earth's orbit

Two small moons in the solar system, known since the 19th century, turn out to be captured asteroids. These two moons are:

Phobos and Deimos around Mars

Which of the following is NOT an accomplishment of the Rosetta mission to Comet Churyumov-Gerasimenko (C-G)?

Rosetta took samples of the surface material of Comet C-G and sent them back to Earth

The comet that broke into more than 20 pieces and then collided with Jupiter in 1994 was

Shoemaker-Levy 9

In 2012, NASA's Spaceguard Survey concluded that astronomers had now identified 90% of the asteroids with diameters greater than 1 km. How could astronomers know that they had reached this goal?

The people doing the survey began to find the same objects over again, indicating they were reaching the limits of their survey

How have astronomers learned what different asteroids are made of?

They examine the spectrum of the sunlight that reflects from the asteroid

Which of the following statements about the tails of comets is FALSE?

a comet always has a nice long tail, even when it is far from the Sun

If there are at least a million asteroids, how did spacecraft like Galileo survive their trip through the asteroid belt?

although there are many asteroids, they are widely spaced (there is lots of space between them)

One of the key reasons that professional astronomers (as opposed to the public) are interested in comets is that they

are icy pieces left over from the time that our solar system formed that can give us clues about that early time

A baseball pitcher wants to impress his girl-friend with how strong his throwing arm is. On which of the following bodies would the pitcher be MOST likely to be able to throw a baseball (a fast ball) so fast it would actually go into orbit?

asteroid Ida

Why were asteroids not discovered until the 19th century?

asteroids are generally small compared to planets and require a good telescope and patient searching to spot them

More than 75% of the known asteroids:

can be found in a belt between Mars and Jupiter

The fact that some asteroids cluster in what are called asteroid families is probably the result of:

collisions which broke up larger bodies into a number of smaller ones

Short-period comets like Comet Halley

come back again and again at predictable intervals

Different asteroids reflect different percentages of the light falling on them. This is due to the fact that they have different:

compositions

Comets get significantly brighter in our skies as they approach the Sun because a. they reflect more sunlight as they get closer to the source of light b. they get bigger as the ice evaporates c. they get closer to the Earth than when they were outside the orbit of Mars d. they move faster and faster e. more than one of the above

e. more than one of the above

Astronomers have realized that the surface of Ida is older than the surface of Gaspra. How do they measure this?

from counting craters on each asteroid's surface

A main difference between asteroids and comets is that asteroids are mostly made of rock and comets are mostly made of

ice

Which of the following statements about the unusual object Chiron is FALSE?

it is one of the largest asteroids, just a little smaller than Vesta

In addition to hundreds of smaller objects they have been discovering in the Kuiper Belt recently, astronomers were surprised to find

larger bodies, with sizes as big as Pluto (now called dwarf planets)

Astronomers estimate that there may be a trillion (a thousand billion) comet nuclei orbiting beyond Pluto. Why then do we not see more comets in our skies?

most comets remain in stable orbits beyond Pluto, only a few have their orbits disturbed and come into the inner solar system

If our estimates of the number of comets in every part of the solar system are correct, the total mass contained in comets must be:

on the order of the mass of all the planets put together

One reason we know more about the surface composition of the asteroid Vesta than about most other members of the asteroid belt is that

pieces of Vesta have landed on Earth as meteorites

The large reservoir of comet nuclei far beyond Pluto, from which we believe new long-period comets come into the inner solar system, is called:

the Oort Cloud

According to astronomical tradition, who gets to suggest the name for a newly discovered asteroid?

the discoverer of the asteroid

Comets change as they approach the Sun in their orbits. Which of the following statements about a comet approaching the Sun is FALSE?

the gravity of the comet nucleus holds on to the evaporated material, and it all eventually freezes back into the nucleus

Which part of a comet is the DENSEST?

the nucleus

Halley's Comet was given that name because Edmond Halley was

the scientist who pointed out that the orbit of the comet was such that it should return every 76 years or so

When larger fragments of Comet Shoemaker-Levy 9 crashed into Jupiter in 1994,

they exploded in Jupiter's atmosphere, releasing energy equal to millions of megatons of TNT