General Asteroid Information

Asteroids are small metallic, rocky lumps that orbit the sun but are not large enough to be considered planets. Asteroids lack an atmosphere.

The majority of asteroids live in the main asteroid belt, a circular asteroid racetrack between Mars and Jupiter that is approximately two to four astronomical units (AU) from the sun. Most main belt asteroids have a stable, slightly elliptical orbit, usually taking between three and six years to circle the sun.

The theory on the existence of asteroids is that had the gravitational pull of Jupiter not been so strong, the asteroids within the asteroid belt would have formed one conglomerated mass and eventually into a planet with an orbit between Mars and Jupiter. It is estimated that the collective mass of all the asteroids is 930 miles (1,500 kilometers) in diameter, under half the size of the moon.

There are three major characterizations of asteroids, which are determined by composition, albedo, and similarity to meteoric samples:

Near-Earth Asteroids

Asteroids which come within 1.3 AU of the Sun are considered near-Earth asteroids. It is assumed that these asteroids have been knocked free from the main belt due to asteroid collisions or the gravitational influence of the planet Jupiter, or are the remnants of short-period comets. The largest known near-Earth asteroid is Ganymed, with an approximate diameter of 25.5 miles (41 kilometers).

There are three main characterizations of near-Earth Asteroids, named for famous examples of each:

Interesting Stuff

Several asteroids are confirmed to have moons orbiting them, including Ida (which the spacecraft Galileo took photographs of in a 1993 fly-by -- the moon was named Dactyl), and Eugenia (which was confirmed by the Canada-France-Hawaii Telescope on Mauna Kea in 1999). This discovery allows observers to make more concise estimates of mass because of the gravitational relationship between the primary asteroid and its moon. These new observations have shown that many asteroids are far less dense than previously thought.
Asteroid was one of the artist names Johan Billing used (for a short period) during his time in Swedish electronic music band S.P.O.C.K.

It replaced the rather odd name Hemoroid, which he held only for a short time immediately after joining the band in 1994; and Asteroid later evolved into Plasteroid, which was the name that he finally settled on and kept until he left the band in 1998.

Asteroids are not round little globes that hurtle through space. A few of the largest ones are, but for the most part, they are encrusted with craters and shaped like potatoes or peanuts, irregular little wedges of iron or stone.

Also, I would like to point out the discrepancies that Hollywood sci-fi movies have managed to turn into widely believed myths.

  • You cannot knock an asteroid out of its path by nuking it. If an asteroid is on a direct collision course with earth, nuking it will simply leave us to deal with a cluster of smaller rocks, which are just as treacherous.
  • There is always a scene where the gallant hero steers the spacecraft out of the path of menacing rocks as they fly through an asteroid belt. You’ll witness asteroids flying this way and that, thousands at a time just waiting to collide with the earthlings’ ship.. but in reality, space is so vast that if you were in the middle of an asteroid belt, you’d be hard pressed to observe one or two asteroids with the naked eye.

Picture: A dark lonely night in Sicily. A lonely monk, Giuseppe Piazzi awake after midnight festivities for the 1st of January, 1801 checks his telescope one last time before bed. His interest is aroused by a small pinprick of light that he is unable to identify....

He named this light Ceres, after the pagan goddess of Sicily (!!!) and after finding a few more, he correctly labelled these objects, planetoids.

But 1802 saw William Herschel, who was slightly more famous due to his earlier discovery of Uranus, call these same objects, which to him looked like small stars, asteroids. However correct Giuseppe might have been in his naming of these leftover chunks of rock floating in space, the influence of William was stronger, and to this day we call them Asteroids.

As"ter*oid (#), n. [Gr. starlike, starry; star + form: cf. F. ast'eroide. See Aster.]

A starlike body; esp. one of the numerous small planets whose orbits lie between those of Mars and Jupiter; -- called also planetoids and minor planets.


© Webster 1913.

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