2 chapter 13 & 14

According to this graph, the minimum size of an object that could cause a mass extinction is a little less than

10km

is the dusty atmosphere of a comet created by sublimation of ices in the nucleus when the comet is near the Sun

A coma

is the solid portion of a comet, and the only portion that exists when the comet is far from the Sun.

A nucleus

is one of two tails seen when a comet passes near the Sun (the other is the dust tail). It is composed of ionized gas blown straight outward from the Sun by the solar wind.

A plasma tail

Leftover planetesimals that formed inside the frost line are known as

Asteroids

Leftover planetesmials that formed inside the frost line are known as

Asteroids

Leftover planetesimals that formed inside the frost line are known as

Comets

The objects that are sometimes visible in the night sky with long tails are

Comets

Based on this graph, which statement below most accurately describes the impacts we should expect on Earth during the coming year?

Earth will be hit by at least one object a few meters in diameter, along with many smaller objects.

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

Ice

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

Extends from about beyond the orbit of Neptune to about twice the distance of

Kuiper belt

The asteroid belt is located between the orbit of

Mars and jupiter

consist of particles shed by comets as they orbit the Sun

Meteor showers

Pieces of asteroids that have fallen to Earth are called

Meteorites

Pieces of asteroids that have fallen to earth are called

Meteorites

Did a large terrestrial planet ever form in the region of the asteroid belt?

No, because Jupiter prevented one from accreting

About a trillion comets are thought to be located far, far beyond Pluto in the

Oort Cloud

Why didn't a planet form in the region of the solar system now occupied by the asteroid belt?

Orbital resonances with Jupiter disrupted orbits in this region

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

Shoemaker-Levy 9

is the comet-rich region of our solar system that spans distances of about 30-100 AU from the Sun

The Kuiper belt

is a huge, spherical region centered on the Sun, extending perhaps halfway to the nearest stars, in which trillions of comets orbit the Sun with random inclinations, orbital directions, and eccentricities

The Oort cloud

The red line on this graph is based on impact rate data and the number of comets and asteroids that pass near Earth. We can use this line on the graph to determine

The typical time between impacts for an object of any size

What is the probability that an object 100 meters in diameter will hit Earth during the coming year?

about 1 in 1000

According to the graph, an object 10 kilometers across hits Earth

about once every 100 million years

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

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

compositions

Ceres, Pluto, and Eris are all round in shape and classified as

dwarf planets

A comet entering the inner solar system from afar will

form a coma and some time later form a tail

The Kuiper belt is located

from about the orbit of Neptune to about twice Neptune's distance from the Sun

The Oort cloud is located

in a spherical region far beyond the orbit of Pluto

The comets of the Oort cloud are thought to have formed

in the same region as the jovian planets

Meteors can be viewed only

on worlds with atmospheres

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

Which part of a comet is the DENSEST?

the nucleus

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

the tail of a comet can sometimes be ahead of the comet in its orbit