What are asteroids?
An asteroid is a large rock in outer space. Some,
like Ceres, can be very large, while others are as small as a grain
of sand. Due to their smaller size, asteroids do not have enough
gravity to pull themselves into the shape of a ball.
Astronomers group asteroids into different categories based on the
way they reflect sunlight.
The asteroid belt is divided into an inner belt
and an outer belt. The inner belt, which is made up of asteroids that
are within 250 million miles (402 million km) of the Sun, contains asteroids that are
made of metals.
The outer belt, which includes asteroids 250
million miles (402 million km) beyond the Sun, consists of rocky asteroids. These
asteroids appear darker than the asteroids of the inner belt, and are
rich in carbon.
Where did the Asteroid Belt come from?
Asteroids are left over materials from
the formation of the Solar System. These materials were never
incorporated into a planet because of their proximity to Jupiter's
strong gravity.
How many asteroids are there?
26 very large asteroids have been
discovered, which is probably most of the big ones. But there are
still millions of smaller ones that we have yet to see because they
are too tiny, only a mile or so across.
If we stuck all the asteroids
together, how big would the new planet be?
If all the materials of all the
asteroids were squashed up into one planet it would be smaller than
our moon.
While most asteroids can be
found in the Asteroid Belt, others are in strange orbits straying far
from home. It is currently believed that at least 5000 asteroids
cross the Earth's orbit, some coming very close. Don't worry though,
asteroids and comets only hit the Earth every 100 million years or so.
Quaoar
Quaoar is the largest known non-planet
object in the Solar System. It is one tenth the size of the
Earth, and is larger than all other asteroids put together.
No picture currently available
Ceres
For many years Ceres was thought to be the
biggest asteroid in the Solar System. It is about 600 miles wide and
contains about 25% of the mass of all the asteroids combined.
However, in the summer of 2001 scientists discovered an even bigger
asteroid orbiting the Sun near Pluto.
No picture currently available
2001 KX76 The New
Asteroid King
On August 23, 2001, astronomers announced the
discovery of a new asteroid. The new asteroid is even bigger
than Ceres, which for over two hundred years had been thought to be
the largest asteroid in the Solar System.
It was discovered looking at old photographs
taken of the sky.
Ida and Dactyl
Ida is a neat little asteroid about 36 miles
wide. It is unique because it has its own little moon called Dactyl.
