Asteroid

Asteroid
A rocky orbiting the sun. Most asteroids are distributed between the orbits of Mars and Jupiter, although some have eccentric orbits that intersect the Earth’s.

There are may be as many as a million with diameters in excess of a kilometer.

The first to be discovered – by Piazzi in 1801 – was the largest, Ceres.

Three more, including Pallas and Vesta, were discovered in the same decade. Eros was discovered on 1898, was the first whose orbit was sufficiently eccentric to extend almost as far as the Earth’s.

The discoverer of Pallas and Vesta, Heinrich Olbers, suggested that the asteroids might be the debris of a*planet shattered by some kind of disaster.

The notion was encouraged by Bode’s law, a mathematical sequence published in the 1770s that correspond to the proportional orbital distances of the known planets, except for a gap between Mars and Jupiter.

The alternate explanation of their origin – preferred by most twentieth century theorists – is that a scattered ring of matter never condensed into a planet for lack of an appropriate nucleus.

Most asteroids are almost entirely metallic, their dominant components being nickel and iron, but some smaller ones are formed out of stony materials like those in the Earths crust, including some carbon compounds.
Asteroid