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- Did you know that our solar system
is made up of more than just the Sun, planets, and moons.
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Our solar system has lots of small bodies
made up of tons of rocky fragments
that orbit the Sun just like the planets.
In fact, you could say that our whole solar system rocks.
These small bodies aren't all the same.
But how do you tell the difference?
Let's talk to a rock star from NASA
to see what makes each of these objects unique.
- Yeah, so asteroids, comets, and meteorites--meteors
are all very different objects.
Most of the asteroids that we see
are basically rock, clays-- some are metal.
And they didn't get large enough to form a planet,
so we classify them as asteroids.
Most of them are found in the asteroid belt
in between Mars and Jupiter.
Comets, on the other hand,
form much further out in the solar system.
We call it the Kuiper belt,
which is past the orbit of Neptune,
and out towards Pluto.
So comets, we think, formed much further out
and thus, are very cold objects.
They've got ice, a lot of ice.
They also have rocks and organic material as well.
So asteroids are the remnants of
the earliest part of the solar system,
that formed about 4.6 billion years ago.
The first materials that condensed into rocks,
called chondrules, basically came together
in little blebs and gradually grew into larger bodies.
The interesting thing about asteroids is that
they never grew large enough to form a planet.
And the reason for that is because
you had Jupiter, which is a giant--a gas giant,
basically causing all these gravitational disruptions.
So you have material coming together and breaking apart
between Mars and Jupiter.
And so that asteroid belt
really was never able to come together.
They range in size, you know,
from a few meters to several hundred meters
in diameter--
even larger, hundreds of kilometers in some cases.
We estimate that there are probably
1 million to 2 million objects
with diameters greater than a kilometer
out in the asteroid belt.
There are certainly much smaller asteroids as well.
And we're discovering them every day.
So most asteroids that we observe in our solar system
have kind of an irregular
polygon, like a spheroidal shape.
So it looks something like a top that you might spin.
And, in fact, asteroids do spin
at various rates.
But there are unusual asteroids as well.
We recently had one that came from interstellar space.
It passed through our solar system,
and it looked like a cigar shape,
so very unusual.
- So it seems like asteroids
come in different shapes and sizes.
And with more than 700,000 asteroids
orbiting the Sun, our solar system
is a lot more crowded than I thought.
For "Real World," I'm Mishay.
Rock on.
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