Asteroids are minor planets that are not comets. They include small solar system bodies and dwarf planets. They are often sometimes referred to as planetoids. Asteroids are the small body in the inner solar system out to the orbit of Jupiter. The small objects in the outer solar system are called comets because of their volatile-based surfaces.
There are millions of asteroids within the young Sun’s solar nebula that never grew large enough to become planets. Most of the asteroids orbit in the asteroid belt between the orbits of Mars and Jupiter or co-orbital with Jupiter. However other orbital families exist.
There are three main groups of asteroids, C-type, S-type, and M-type. They are generally identified and named with carbon-rich, stony and metallic compositions respectively.
The first asteroid was discovered in 1801 by Giuseppe Piazzi. It was initially considered to be a new planet. This was followed by the discovery of eight similar bodies. Since the discovery of the first asteroid, methods have dramatically improved.
Unit 1998 asteroids were discovered in a four step process; The region of the sky was photographed with a wide-field telescope a few hours apart, the two films of the same region were viewed under a stereoscope, once a moving body was identified its location would be measured precisely using a digitizing microscope, and lastly a computer program determined whether an apparition ties together earlier apparitions into a single orbit. Today the discovery of asteroids is completely computerized.
Since the invention of space travel, asteroids and asteroid belts can be examined. Before said time, asteroids were merely dots of light on the largest telescope. Now the shapes and terrain can be studied.