ASTEROIDS

In the 1766 a formula was developed that gives the approximate mean distances of the known planets from the Sun. This is known as Bode's Law. However there was an apparent gap in the series between the distances of Mars and Jupiter. It was thought there was a missing planet. In 1801 Ceres was discovered and thought to be the missing planet. But this small planet was only 770 km in diameter. Then in 1802, Pallas was discovered, another small planet. Juno was discovered in 1804, Vesta in 1807, and Astraea in 1845. Thousands of small orbits were found in a similar orbit. These minor planets are called asteroids. There are two ways in which asteroids may have developed. They were either a planet that never developed or a planet that broke up.

Asteroid Ida with a small moon called Dactyl was identified by the Galileo spacecraft in 1993.