What is a planet?

The International Astronomical Union defines a planet as a celestial body that:

  1. It must orbit a star
  2. It must have enough mass to generate so that its self-gravity draws it into a (nearly) spherical
  3. It has enough gravity to have cleared smaller objects out of its orbit

Return to syllabus

In case you ever feel lost, or want to jump, here’s a map.

Notes mentioning this note

Here are all the notes in this garden, along with their links, visualized as a graph.