Astronomy ch. 9

On average, how often should an asteroid or comet strike Earth with as much energy as that of a hydrogen bomb (like the Tunguska impact)?
Once a century
What is Charon thought to have in common with our own Moon?
Both probably formed as a result of giant impacts
Why won't Pluto collide with Neptune?
Pluto orbits the Sun exactly 3 times for every 2 Neptune orbits, which ensures the two planets never come close together.
Suppose we discover a new comet on an orbit that brings it closer to the Sun than Mercury every 125 years. What can we conclude?
It has been on its current orbit for only a very short time compared to the age of our solar system.
Suppose there were no solar wind. How would the appearance of a comet in our inner solar system be different?
It would have only one tail instead of two
Which of the following objects are probably NOT located in the same region of the solar system in which they originally formed?
Oort cloud comets
Suppose you find a meteorite made almost entirely of metal. According to current theory, which of the following statements must be true?
Your meteorite is a fragment from the core of a large asteroid that had undergone differentiation and then was shattered by a collision.
How can we determine the reflectivity of an asteroid?
By comparing its brightness in visible light to its brightness in infrared light.
Gaps in the asteroid belt (often called Kirkwood gaps) are caused by ______.
orbital resonances with Jupiter.
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.
If we could put all the asteroids together, their total mass would be ______.
much less than the mass of any terrestrial planet.
How does the largest asteroid, Ceres, compare in size to the planets?
It is about half the diameter of Pluto, the smallest planet.
What do asteroids and comets have in common?
Most are unchanged since their formation in the solar nebula.
How do asteroids differ from comets?
Asteroids are made of rocky material. Comets are made of icy material.
A rocky leftover planetesimal orbiting the Sun is
an asteroid.
An icy leftover planetesimal orbiting the Sun is
a comet.
Why do asteroids and comets differ in composition?
Asteroids formed inside the frost line, while comets formed outside.
What is the size of the largest asteroid?
1,000 km
Which is closest to the average distance between asteroids in the asteroid belt?
1 million km