Mike Brown

The size of Planet Nine, next to Earth and Neptune. PlanetUser/Wikimedia Commons, CC BY-SA 4.0

Why Astronomers Are Arguing Over ‘Planet Nine’, Which They Haven’t Observed Yet

An artist's depiction of a Kuiper Belt Object. Credit: NASA

Does the Solar System Really Have a Ninth Planet?

This artistic rendering shows the distant view from Planet Nine back towards the sun. The planet is thought to be gaseous, similar to Uranus and Neptune. Hypothetical lightning lights up the night side. Caption & image credit: Caltech/R. Hurt (IPAC)

Caltech Astronomers Build Evidence for a Ninth Planet Beyond Pluto