astronomy chapter 12

The total number of comets orbiting the Sun is estimated to be about ______.

1 trillion

what is eris?

An icy object that orbits in the Kuiper belt and is more massive than Pluto

Which best describes the primary difference between asteroids and comets?

Asteroids are rocky and comets are ice-rich.

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

Comets always have tails.

Why isn't there a planet where the asteroid belt is located?

Gravitational tugs from Jupiter prevented material from collecting together to form a planet.

Which statement about asteroids is not true?

If we could put all the asteroids together, they would make an object about the size of Earth.

the _____ extends from about beyond the orbit of Neptune to about twice the distance of Neptune from the Sun.

Kuiper belt

Which of the following statements is not true?

Objects in the Kuiper belt are made mostly of rock and metal.

Why aren't small asteroids spherical in shape?

The strength of gravity on small asteroids is less than the strength of the rock.

According to current evidence, Pluto is best explained as ______.

a large member of the Kuiper belt

Part complete A rock found on Earth that crashed down from space is called ______.

a meteorite

What do we mean by a primitive meteorite?

a meteorite that is essentially unchanged since it first condensed and accreted in the solar nebula almost 4.6 billion years ago

Listed following are several objects in the solar system. Rank these objects from left to right based on their distance from the Sun, from closest to farthest.

a typical asteroid in the asteroid belt a typical Kuiper belt object a typical Oort cloud object

Listed following are several objects in the solar system. Rank these objects from left to right based on their orbital period around the Sun from shortest to longest.

a typical asteroid in the asteroid belt a typical Kuiper belt object a typical Oort cloud object

Listed following are several objects in the solar system. Rank these objects from left to right based on the distance from the Sun at which they are presumed to have formed, from nearest to farthest.

a typical asteroid in the asteroid belt a typical Oort cloud object a typical Kuiper belt object

Where are the Trojan asteroids located?

along Jupiter's orbit, 60° ahead of and behind Jupiter

Which direction do a comet's dust and plasma tails point?

away from the sun

Among discovered meteorites, we have found some with all the following origins except _________.

being a fragment from Comet Halley

The asteroid belt is located ______.

between the orbits of Mars and Jupiter

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

coma

asteroids

compositions similar to that of the terrestrial planets typically orbit the Sun at approximately 3 AU

A comet entering the inner solar system from afar will __________.

form a coma and some time later form a tail

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

Halley's comet is named after the English scientist Edmund Halley (1656-1742) because ______.

he calculated its orbit and predicted the year in which it would next be seen.

Particles ejected from a comet can cause a(n) _______ on earth

meteor shower

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

nucleus

If the hypothesis tracing the extinction of the dinosaurs to an impact is correct, the dinosaurs died off largely because ______.

of global climate effects initiated by dust and smoke that entered the atmosphere after the impact

A comet's plasma tail always points directly away from the Sun because __________.

of pressure exerted by the fast-moving charged particles in the solar wind

Objects the size of the one that exploded over Chelyabinsk (Russia), causing significant damage, probably hit Earth at least __________.

once a century

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

oort cloud

The large gaps in the asteroid belt (often called Kirkwood gaps) are caused by

orbital resonances with Jupiter.

A typical meteor is created by a particle about the size of a _________.

pea

A comet's ______ stretches directly away from the Sun.

plasma tail

During the time that a comet passes through the inner solar system, the comet can appear quite bright because __________.

sunlight reflects off the comet's tail and coma

When a comet passes near the Sun, part of it takes on the appearance of a large, bright ball from which the tail extends. This part is called _____.

the coma

What do we mean by a mass extinction?

the extinction of a large fraction of the world's plant and animal species in a relatively short period of time

What is Charon?

the largest of Pluto's three known moons

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