Minor Planets - The Discovery Of Asteroids, Main-belt Asteroids, Beyond The Main Belt, The Collision Threat

There are many thousands of minor planets, also termed miniplanets or asteroids, within our solar system. They vary in size from a foot or so in diameter to hundreds of miles in diameter. The majority of asteroids, the main-belt asteroids, circle the Sun in a donutshaped region between the orbits of the planets Jupiter and Mars. Several other asteroid families have been identified, including a large population of objects beyond the orbit of Neptune termed the Kuiper belt and approximately 70 objects, the Plutinos, that circle the Sun on remote, elliptical orbits resembling Pluto's. Controversy has raged among planetary astronomers in recent years over whether Pluto itself should be counted as a large asteroid rather than as a true planet. There is also a significant population of asteroids having orbits which cross, or come near to crossing, that of Earth; these are termed near-Earth asteroids (NEAs).