What makes a planet?
The International Astronomical Union says a planet must do 3 things: 1. It must orbit a star. 2. It must be big enough to have enough gravity to force it into a spherical shape. 3. It must be big enough that its gravity cleared away any other objects of a similar size near its orbit around the Sun.
Join Alexa Answers
Help make Alexa smarter and share your knowledge with the worldLEARN MORE