Astronomers are proposing a new, more quantitative definition of what makes a planet. The new definition looks more directly at the object's mass — but it would still leave Pluto out of the running.

In 2020, a team of researchers found something surprising in the high clouds of Venus. Earth-based telescopes detected the spectral signature of phosphine, a simple molecule that should have no ...

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 ...