The International Astronomical Union defines a planet as a celestial body that orbits the sun, is massive enough that gravity has forced it into a spherical shape, and has cleared away other objects ...

In our solar system, objects are close enough that we can check the orbit and see if has been cleared of other objects. This is problematic if we can only infer rough properties of what could be a ...

The proposal refines current definitions that require planets to be round bodies which orbit our sun and have ‘cleared’ their neighbourhoods Planetary scientists are proposing a new definition for ...

SpaceX has made trips to orbit routine. Satellites in orbit are vital to the modern world. Here's what you need to know about how we send things whizzing around the Earth. Stephen Shankland worked at ...