Ida and its moon
Asteroid Belt Facts:
- The total weight of all
the asteroids in the asteroid belt is about 1/35th of that of our moon!
largest asteroid, called Ceres, makes about 1/3 of the total weight of all the
asteroid belt lies between Mars and Jupiter. It contains lumps of rock much smaller
than planets. These lumps are called asteroids or minor planets. They are not
visible from Earth with the naked eye, but many may be seen through binoculars
or small telescopes.
big are the asteroids?
largest asteroid is Ceres, which is 1032 kilometers across. The next largest,
which is called Pallas, is 588 kilometers across. Asteroids less than a kilometer
across have also been seen. Unofficially the limit has been set at 50 meters,
and anything smaller than that is going to be simply called a meteoroid. With
advances in telescopes and particularly for objects that travel close to the Earth,
some objects have been seen that are indeed smaller than 50 meters that merely
pass nearby the Earth.
many are there?
are probably several million asteroids in the solar system. Over 96,000 asteroids
have been given numbers. Almost 12,000 of them have names. But even though there
are a lot of asteroids, the asteroid belt is mostly empty space. Traveling through
the asteroid belt in a space ship would not be very much like what you see in
a science fiction film.
are they named after?
first asteroids were named after mythical heroes and gods much like the major
planets. The first to be discovered was named Ceres after the Roman goddess of
growing plants (particularly grain) and of motherly love. The second asteroid
discovered was called Pallas named after one of the Greek gods of wisdom. Asteroids
are also given a number in the order of their discovery, so Ceres is 1, Pallas
is 2, and so forth. As the number of known asteroids increased, the supply of
mythical names was exhausted so names from other sources were used.
asteroids were named after countries. For example asteroid number 136 is named
Austria. Others were named after plants, for example 978 Petunia. 1620 Geographos
was named after the National Geographic Society, in recognition to their efforts
at sharing knowledge about the Solar System. Many are named after people both
alive and dead. In a couple of cases, like 2309 Mr. Spock, asteroids were named
after the discover's pet cat. This naming has been discouraged, but it still happens
occasionally. Even fictional characters have been used.
names for asteroids can be suggested by the people who discover them. The names
become official after a group of people reviews them to make sure they are not
offensive or too much like another name. Due to some automated asteroid scanning
observatories and a systematic exploration of the Solar System for near Earth
asteroids, most new asteroid discoveries are not even getting a name at all, but
rather a numerical designation, and it is not anticipated that they will ever
be given a formal name, at least in this century.
first asteroid to be discovered was Ceres, on 1 January 1801, by Giuseppe Piazzi
on accident. At first he thought this was a comet, then later a planet! When it
was realised it was too small Sir William Herschel (the astromoner who discovered
Uranus) made up the word "asteroid" to describe it, from the Latin word aster
meaning star and the -oid meaning rock or planet. In other words a star-like
planet because he couldn't see any details due to the small size of the object.
By 1807 another 3 asteroids were discovered, but no more were found until 1830
when a persistent asteroid hunter named Karl Ludwig Hencke found a fifth and sixth
asteroids. Ever since then at least one new asteroid has been found each year.
1891 the first pictures of the night sky were taken to find more asteroids. This
led to the discovery of many more asteroids. A picture of the same part of the
sky is taken on two different nights. When the two pictures are compared, any
asteroids will have changed their location on the image compared to the stars.
our modern times, over 280,000 asteroids have been discovered. Many more are being
found all the time. Some of these asteroids pass near the earth and astronomers
want to find any that come close to our planet.
are they made of?
asteroids (3 out of 4) are made of carbon-based rock. The rest are made of the
metals iron and nickel. About half of these are pure iron and nickel; the rest
are mixed with silica compounds. Each of the larger metal asteroids contains more
iron than has been mined in the entire history of human kind.
are very interested in what asteroids are made of because it can help them learn
how the solar system was formed. Several spacecraft have visited asteroids to
learn more about them.
there asteroids outside of the asteroid belt?
asteroids are found in the asteroid belt, but not all. Some asteroids orbit closer
to the Sun. Asteroids that closely approach Earth are called Near-Earth Asteroids.
Sometimes they strike the Earth, burning in the atmosphere as a meteor. If they
are large enough, they might actually hit the surface and become meteorites.
are also some asteroids in the outer solar system that are called Centaurs, although
it is hard to determine whether a particular Centaur is an asteroid, comet, or
Kuiper Belt object. For example, the first Centaur to be discovered was Chiron.
But some scientists think it is a comet, not an asteroid. Officially it is both
the asteroid 2060 Chiron and the comet 95P/Chiron!
asteroids are also found at the stable points 60° behind and ahead of the orbits
of Jupiter and other planets. The points are called Lagrange points and the asteroids
found there are called Trojans. Many of the small moons of some planets may have
once been asteroids that were captured by the planet's gravity when they came