Astro 3 Chapter 9

False The total mass of the asteroids is much less than the mass of a terrestrial planet.

between the orbits of Mars and Jupiter

a meteorite

pea We do not see the particle itself, but rather the flash of light it generates as it enters (and burns up in) the atmosphere at high speed.

a meteorite that is essentially unchanged since it first condensed and accreted in the solar nebula some 4.6 billion years ago It's called primitive because the word means "first."

being a fragment from Comet Halley No such fragments are known and they are unlikely to exist, since comet fragments should be ice that would burn up as they passed through our atmosphere.

false Only the rare comets that enter the inner solar system have tails, and only when they are close to the Sun.

generally away from the Sun They are pushed away from the Sun by radiation and the solar wind.

the coma The coma is essentially a large atmosphere of gas and dust released by the comet.

1 trillion This number is estimated by counting the number of comets that we see in the inner solar system and then calculating how many must exist in the Oort cloud in order to account for those that we see.

a large member of the Kuiper belt And it is not even the largest known member, as an object discovered in 2005 is larger.

An icy object that orbits in the Kuiper belt and is more massive than Pluto It is the largest known member of the Kuiper belt (as of 2007) and is officially classified as the largest known dwarf planet in our solar system.

the largest of Pluto's three known moons It is much larger than the other two moons of Pluto, and is thought to have formed in a giant impact with Pluto (much as our own Moon is thought to have formed in a giant impact with Earth).

the extinction of a large fraction of the world's plant and animal species in a relatively short period of time Several mass extinctions have been detected in the fossil record, including the one that wiped out the dinosaurs.

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

once a century This is one reason why many people advocate a more careful search for potential impact threats

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

much less than the mass of any terrestrial planet

Gravitational tugs from Jupiter prevented material from collecting together to form a planet. Early in the solar system's history there should have been plenty of material to form a planet here, but Jupiter's gravity prevented it. Over time, most of this material has left this region (crashing to other planets or ejected from solar system), leaving the asteroid belt of today with much less mass than would be needed to form a planet.

orbital resonances with Jupiter

the glow from a pea-size particle and the surrounding air as the particle burns up in our atmosphere

The rings of Saturn The rings consist of countless small particles ranging in size from dust grains to city blocks, so it would be quite a challenge to doge them.

Your meteorite is a fragment from the core of a large asteroid that shattered in a collision. Only a large asteroid would have undergone differentiation to make a metal core, so this must be the source of the meteorite.

Oort cloud comets Oort cloud comets probably formed between the jovian planets are were kicked out to their current large distances from the Sun.

It would have only one tail instead of two. There would be no plasma tail without the solar wind. The dust tail would still be present, since it responds to radiation pressure rather than the solar wind.

It has been on its current orbit for only a very short time compared to the age of our solar system. Comets cannot survive more than a couple hundred passages through the inner solar system because they lose mass with each pass. So this comet cannot have been on its current orbit for more than a few tens of thousands of years.

Earth is crossing the orbit of a comet

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

It probably formed as a result of a giant impact. That seems to be the most likely explanation for Charon's relatively large size in comparison to Pluto, and the giant impact may also explain the two smaller moons of Pluto.

Even at its closest, Pluto is still well beyond the orbit of Uranus, and comets grow tails only when they come within a few AU of the Sun.

Fossilized dinosaur bones contain fragments of rock from the impact. We do not see any such thing

To try to prevent an impact that might destroy a town or city. The hope is that if we can first identify potential threats, then we can find a way to divert their paths before they hit Earth.

Neither the asteroid belt nor Oort cloud would exist. Jupiter's gravity is responsible for the existence of the asteroid belt, and the Oort cloud is thought to consist of comets ejected from the region of the jovian planets by their gravity. So without the jovian planets, neither the asteroid belt nor the Oort cloud would be likely to exist.