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Astronomy – Solar Debris
Kowinsky
NAME: _________________________
Pd: _________
Asteroids
There are millions, of small rocks that orbit the Sun,
most of them between the orbits of Mars and Jupiter. A plot
of the known asteroids is available at the Minor Planet
Center. About one million of them are larger than 1
kilometer across. Those smaller than about 300 kilometers
across have irregular shapes because their internal gravity is
not strong enough to compress the rock into a spherical
shape. The largest asteroid is Ceres with a diameter of 1000
kilometers. Pallas and Vesta have diameters of about 500
kilometers and about 15 others have diameters larger than
250 kilometers. The number of asteroids shoots up with
decreasing size. The combined mass of all of the asteroids is
less than the Moon's mass. Very likely the asteroids are
pieces that would have formed a planet if Jupiter's strong
gravity had not stirred up the material between Mars and
Jupiter. The rocky chunks collided at speeds too high to
stick together and grow into a planet.
Though there are over a million asteroids, the volume of space they inhabit is very large, so they are far apart
from one another. Unlike the movie The Empire Strikes Back, where the spacecrafts flying through an asteroid
belt could not avoid crashing into them, real asteroids are at least tens of thousands of kilometers apart from
each other. Several spacecraft sent to the outer planets have traveled through the asteroid belt with no problems.
Classification
In addition to classifications of asteroids based on their orbits, most asteroids fall into three classes based on
composition. The C-type or carbonaceous are greyish in color and are the most common, including more than
75 percent of known asteroids. They probably consist of clay and stony silicate rocks, and inhabit the main
belt's outer regions. The S-type or silicaceous asteroids are greenish to reddish in color, account for about 17
percent of known asteroids, and dominate the inner asteroid belt. They appear to be made of silicate materials
and nickel-iron. The M-type or metallic asteroids are reddish in color, make up most of the rest of the asteroids,
and dwell in the middle region of the main belt. They seem to be made up of nickle-iron. There are many other
rare types based on composition as well — for instance, V-type asteroids typified by Vesta have a basaltic,
volcanic crust.
Earth Impacts
Dozens of asteroids have been classified as "potentially hazardous" by the scientists who track them. Some of
these, whose orbits come close enough to Earth, could potentially be perturbed in the distant future and sent on
a collision course with our planet. Scientists point out that if an asteroid is found to be on a collision course with
Earth 30 or 40 years down the road there is time to react. Though the technology would have to be developed,
possibilities include exploding the object or diverting it.
For every known asteroid, however, there are many that have not been spotted, and shorter reaction times could
prove more threatening.
Asteroids: Ida, Vesta, and Itokawa
Questions based on reading:
1.) Old theories about the origin of the asteroid belt suggest it was a planet that broke apart. According to
this article, what does it suggest about modern theories on the origin of the asteroid belt?
2.) If you were to fly a spacecraft through the asteroid belt, would you have to worry about hitting an
asteroid? Why or why not?
3.) Without looking at an image of Ceres, what can you predict about the shape of this asteroid?
4.) Using information you know about shepherd moons, make an analogy between Jupiter, Mars, and the
asteroid belt.
5.) If Jupiter’s gravity can hold the Trojan asteroids in its orbit, do you think other planets can have similar
groupings of asteroids in their orbits? If so, what would be different about the groupings of asteroids?
6.) There are 3 general types of asteroids, C, S, and M. What is the composition of each type? Which type
is the most common, and which type is the rarest?
C:
S:
M:
7.) What is the asteroid Vesta composed of?
8.) Have all of the asteroids that could be “potentially hazardous” been found?