Space Station Info :: Asteroids


An asteroid is a small, solid object in our Solar System, orbiting the Sun. An asteroid is an example of a minor planet (or planetoid), which are much smaller than planets. Most asteroids are believed to be remnants of the protoplanetary disc which were not incorporated into planets during the system's formation. Some asteroids have moons. The vast majority of the asteroids are within the main asteroid belt, with elliptical orbits between those of Mars and Jupiter.

Space Station AsteroidsThe term "asteroid", meaning star-like was coined in 1802 by Sir William Herschel shortly after Olbers discovered the second one, 2 Pallas, in late March of the same year, to describe their star-like appearance; the other then-known planets all show discs, by comparison.

He also applied that term to the small moons of the giant planets. The first scientific paper to use the word in its title was published in 1840 by Erman.

The exact definition of an asteroid is unsettled. The term "Minor planet" carries no strong suggestion about the composition of the object or its general location in the solar system, and some argue that not every minor planet should be called an "asteroid".

One way to classify asteroids is in terms of size. A working definition is that asteroids are larger than 50 m in diameter, distinguishing them from meteoroids, which are typically boulder-sized or smaller. The distinction is made because asteroids are large enough to survive passage through Earth's atmosphere and strike Earth largely intact while the smaller meteoroids generally break up high in Earth's atmosphere.

Thus, it would be safest to use the term "asteroid" for Solar System objects that are bigger than meteoroids, smaller than planets, and made out of rock, not ice. See Solar System for a complete taxonomy of objects in our system, and minor planet for taxonomy of the sub planetary objects that include asteroids. The term artificial asteroid is sometimes used to designate man-made objects which have ended up in solar orbits, such as the Mariner IV probe.

Also see about

Asteroids In The Solar System
Asteroid Classification
Asteroid Discovery
Asteroid Exploration