How many dwarf planets are in the Solar System?
Officially, there are currently five dwarf planets, though there are some other objects that probably deserve this title, and almost certainly many more to be discovered. In 2006, the International Astronomical Unioninvented the category ‘dwarf planet’ to encompass objects that follow independent orbits around the Sun, are massive enough to pull themselves into a spherical shape (so they’re not asteroids or comets), but which (unlike proper planets) don’t have enough gravity to ‘clear out’ smaller objects from around their orbits. The known dwarf planets are Ceres (the largest body in the Asteroid Belt) and Pluto, Haumea, Makemake and Eris (the last four all icy bodies orbiting in the outer Solar System beyond Neptune).
Answered by Giles Sparrow