How Many Planets Are in the Solar System?May 31st, 2013
Universe Today publisher Fraser Cain explains the official number of planets in our solar system, considering the Astronomical Union’s 2006 definition of what is a “planet.” Eight. There are eight planets in our solar system. Although Pluto used to be considered a planet, giving us nine, it will never be nine planets again. Never.
What criteria must be met to be considered a planet?
- A planet has to orbit the Sun.
- A planet needs enough gravity to pull itself into a sphere.
- A planet needs to have cleared out its orbit of other objects.
Pluto meets numbers 1 and 2, but hasn’t done number 3. So Pluto is considered a “dwarf planet” and not a planet. Our solar system therefore officially has eight planets and five dwarf planets.