chapter 14

The three largest asteroids are:

Ceres, Pallas, and Vesta.

What is so unusual about Pluto's orbit?

It is more inclined to the ecliptic than any of the eight planets.

The following figures show four positions (1-4) of a comet during its orbit of the Sun. Also shown is the orbit of the Earth around the Sun. Rank the positions of the comet from left to right based on the size of its tail, from shortest to longest. (Not to scale; tails not shown.)

The length of the tail depends primarily on the distance of the comet from the Sun. It is longer when the comet is closer to the Sun and shorter (or nonexistent) when the comet is farther from the Sun.

Now that we are aware that asteroids cross Earth's orbit, detecting them has become important. Why are they so difficult to detect if they are crossing Earth's orbit?

They are relatively far away. They are small. They are not very reflective. answer:All of the above.

Asteroids that cross Earth's orbit may eventually collide with Earth. If that were to happen, what could be the result?

They would make huge impact craters. They would kill all life on Earth. They would be destroyed in Earth's atmosphere.

What is the typical size of most known asteroids?

a few kilometers

The body which wiped out the dinosaurs was about:

as big as one of Mars' moons.

The tail of a comet always points:

away from the Sun and becomes longest and brightest at perihelion.

The bright spherical part of a comet observed when it is close to the Sun is the

coma

Listed following are some distinguishing characteristics of comets, meteors, and asteroids. Match these to the appropriate category of objects.

comets: form a coma when near the Sun most are located either in Kuiper belt or Oort cloud visible in the sky as a fuzzy patch of light that rises and sets with the stars Meteors visible in the sky as a bright streak of light for only a few seconds dust particles entering Earth's atmosphere at high speed Asteriods typically orbit the Sun at approximately 3 AU compositions similar to that of the terrestrial planets

Charon's orbit:

is highly inclined to Pluto's orbital plane.

The _____extends from about beyond the orbit of Neptune to about twice the distance of Neptune from the Sun.

kuiper belt

Particles ejected from a comet can cause a(n) _____on Earth.

meteor shower

A comet's sis the frozen portion of a comet.

nucleas

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

oort cloud

A comet's _________stretches directly away from the Sun.

plasma tail

The Oort Cloud is thought to be:

the spherical cloud of comets and some larger icy bodies surrounding the outer solar system.

Meteorites are valuable to astronomers because:

they may provide evidence about the process in which the solar system was born.