9 - asteroids, comets and dwarf planets (nov. 16) Solar system has many objects smaller than the major planets: These orbits show the strong in uence of jupiter"s powerful gravity. Aster = star + oid = body - an object that looks like a star, but it orbits the sun. Largest (known) = 1000 km in diameter. More than 400,000 catalogued asteroids, but many more have been detected. Probably more than 1 million asteroids larger than 1 km. Almost all have nearly circular orbits between mars and jupiter = asteroid belt . A few orbit with jupiter, ahead or following in its orbit - captured by jupiter + sun. Tiny asteroids, too small to detect at a distance - sizes are m, cm, mm, dust. Some meteoroids (speed 30 km/s) hit earth"s atmosphere, heat up (friction), give off a ash of light as they disintegrate.