A proposed planet definition – a planet is a sub-stellar mass body that has never undergone nuclear fusion and that has sufficient self-gravitation to assume a spheroidal shape adequately described by ...

Planets are spherical, and the International Astronomical Union's attempt to make this part of their definition has merit. There was once a prissy British civil servant who, when he came across a ...

This is a fantastic question Lionel, and a really good observation! When we look out at the Solar System, we see objects of all sizes — from tiny grains of dust, to giant planets and the Sun. A common ...