The number of planets that orbit the sun depends on what you mean by “planet,” and that’s not so easy to define ...

Astronomers for the first time have deciphered the three-dimensional structure of the atmosphere of a planet beyond our solar ...

The system is believed to be traveling at least 1.2 million miles per hour (1.93 million kilometers per hour), according to a ...

Feb. 18 marks the 95th anniversary of the discovery of our outermost planet-not-planet. Here's what to know about the short ...

Many of the new planets have a "new terrain system" and that allows for truly towering mountains and even "oceans that can be several kilometers ... planet but it's the size of a real planet?" ...

A planet-size object that possibly once visited the ... (One AU is approximately 93 million miles, or 150 million kilometers, roughly the average distance from Earth to the sun.) ...