Astronomy Chapter 9

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Which of the following statements is NOT true?

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

A rock found on Earth that crashed down from space is called _____.

a meteorite

The asteroid belt is located ________

between the orbits of Mars and Jupiter

Which statement about asteroids is NOT true?

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

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


What do we mean by a primitive meteorite?


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

being a fragment from Comet Halley

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

comets always have tails

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

generally away from the Sun


the coma.

The total number of comets orbiting the sun is estimated to be about ___________

1 trillion

What is Charon?

the largest of Pluto's three moons

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

a large member of the Kuiper belt

What is Eris?

an icy object that orbits in the Kuiper belt and is larger than Pluto.

What was the shoemaker-Levy 9 impact?

the 1994 impact of a chain of comet fragments into Jupiter

What do we mean by a mass extinction?


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



It is a little less than half the diameter of our Moon

If we could put all of the asteroids together, their total mass would be ________.

much less than the mass of any terrestrial planet



Gaps in the asteroid belt (Kirkwood gaps) are caused by __________.

orbital resonances with Jupiter

When you see a bright flash of a meteor, what are you actually seeing?


In science fiction movies, spaceships are often shown dodging through large numbers of closely spaced, boulder size objects. Which of the following real things in our solar system would look most like such science fiction dangers?

the rings of Saturn

Suppose you find a meteorite made almost entirely of metal. According to current science, which of the following statements might be true?



Oort cloud comets


It would have only one tail instead of two.



When we see a meteor shower, it means that _________.

Earth is crossing the orbit of a comet

Why won't Pluto collide with Neptune?

Pluto orbits the Sun exactly two times for every three times Neptune orbits, which ensures that they never come close together.

What is Pluto's moon Charon thought to have in common with our own moon?

It probably formed as the result of a giant impact

Which of the following is NOT a piece of evidence supporting the idea that Pluto is a large comet of the Kuiper belt?

Pluto grows a coma and a long tail when it is at at the point in its orbit closest to the Sun.

The discovery of Eris _________.


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?

Fossilized dinosaur bones contain fragments of rocks from the impacts


Neither the asteroid belt nor Oort cloud would exist.

Facts about asteroids

rocky leftovers of planet formations
largest: Ceres
small asteroids are more common
all of the asteroids together does not equal a terrestrial planet
potato shaped objected
cratered not round

Asteroid orbits:

most asteroids orbit between Mars and Jupiter
Trojan asteroids follow Jupiter's orbit.

Origin of Asteroid Belt

Rocky planetesimals between Mars and Jupiter did not accrete into a planet. Jupiter's gravity with orbital resonance influence stirred up asteroid orbits and prevented their accretion into a planet


something that has already landed.

most meteorites are pieces of asteroids


streak of light as an object falls

Primitive Meteorites:

rock that hasn't changed

Processed meteorites:

younger, have experienced processes like volcanism or differentiation

Comet facts

formed beyond the frost line
dirty snowball
most comets do not have tails
remain perpetually frozen
only comets that enter the inner solar system grow tails


atmosphere that comes from the nucleus


piece of ice

Plasma tail

gas escaping from the coma, pushed by solar wind

Dust tail

pushed by photons

Meteor showers

Comets eject small particles that follow the comet around in its orbit and cause meteor showers when Earth crosses comet's orbit

Oort Cloud

random orbits extending about 50,000 km

not from beginning of solar system.. byproduct of Jupiter... once closer to the sun.. kicked out by gravitational interactions with Jovian planets.

Kuiper Belt

orderly orbits from 30-100 AU in disk of solar system

flat plane, aligned with the plane of planetary orbits, orbiting in the same direction as the planets


Pluto's orbit is tilted and elliptical

Neptune and Pluto prevented collision

Neptune orbits three times during the time Pluto orbits twice.. resonance prevents a collision

Is Pluto a Planet?

not gas- ice
icy composition like a planet
elliptical, inclined orbit
more in common with comets

What is pluto like?

very cold
five moons... largest- Charon
thin nitrogen atmosphere that refreezes onto the surface as Pluto's orbit goes farther from Sun.

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