Asteroids and comets

Millions of small rocky bodies called asteroids are present in the solar system. If asteroids were luminous, we would see as many of them as stars in the night sky. A significant portion of them orbit in a ring between the orbits of Mars and Jupiter, between 2 and 4 AU, known as the asteroid belt.

Billions of small icy bodies called comets travel to the outer reaches of the solar system. Most of them reside in two distant reservoirs: the Kuiper Belt (beyond Neptune, between 30 and 55 AU) and the Oort Cloud (a diffuse sphere extending up to 100,000 AU), from which some are ejected toward the Sun, becoming spectacular with their tails of gas and dust.