Space questions, answered
How many planets are there in the Solar System?
Eight: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Pluto was reclassified as a dwarf planet in 2006.
The count dropped from nine to eight in 2006, when the International Astronomical Union defined a 'planet' as a body that orbits the Sun, is round under its own gravity, and has cleared its orbital neighbourhood of other objects. Pluto shares its region with many other icy bodies, so it became the first of the 'dwarf planets'.
There are at least five recognised dwarf planets — Pluto, Eris, Haumea, Makemake, and Ceres — and likely many more awaiting confirmation in the outer Solar System.
The Atlas of Worlds — all of them, mapped →Fly Pluto's surface →
People also ask
Why is Pluto not a planet?
Because it hasn't 'cleared its orbit' — it shares the Kuiper Belt with countless other icy bodies. It's classified as a dwarf planet.
What is the biggest planet?
Jupiter — more massive than all the other planets combined.
Sources: IAU — 2006 planet definition