Asteroids

n. small object that orbits the sun

Asteroids, also called minor planets or planetoids, are a class of astronomical objects. The term asteroid is generally used to indicate a diverse group of small celestial bodies in the solar system that orbit around the Sun. Asteroid (Greek for "star-like") is the most commonly used word in the English literature for minor planets, which has been the term preferred by the International Astronomical Union; some other languages prefer planetoid (Greek: "planet-like"), because it more accurately describes what they are. In late August 2006, the IAU introduced the term "small solar system bodies" (SSSBs), which includes most objects thus far classified as minor planets, as well as comets. At the same time they introduced the term dwarf planet for the largest minor planets. This article deals specifically with the minor planets that orbit in the inner solar system (roughly up to the orbit of Jupiter). For information on other types of objects, such as comets, Trans-Neptunian objects, and centaurs, see Small solar system body.
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Noun
1. any of numerous small celestial bodies composed of rock and metal that move around the sun (mainly between the orbits of Mars and Jupiter)
(synonym) minor planet, planetoid
(hypernym) planet
(hyponym) Apollo asteroid
(member-holonym) solar system
Adjective
1. shaped like a star
(synonym) star-shaped
(similar) angular, angulate

These are rocky bodies, the vast majority of which orbit the Sun between Mars and Jupiter. Several thousands of asteroids are known to exist but it is thought that there must be around 100,000 in all, most of which are too small or too faint to be detected from the Earth at present. The largest asteroid is named Ceres and has a diameter of 579 miles. The smallest detected asteroids have diameters of several hundred feet. Together with comets and meteroids, asteroids make up the minor bodies of the solar system. They are the left over planetessimals from the formation of the solar system. The vast gravitational pull of Jupiter is thought to have stopped the members of the asteroid belt from forming a planet. Some asteroids travel in eccentric, elliptical orbits which cross the orbit of the Earth. These are known as Earth crossing asteroids. For purposes of cataloging they are numbered sequentially as they are discovered.

ASTEROIDI. PIANETINI. STELLE DI MARE