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

More than 1 million "interstellar objects" the size of the Statue of Liberty could be drifting unseen in the outer solar ...

Pluto may not be a planet any more, but you still have a chance to see the distant dwarf planet at one of Michigan's ...

Explore Ceres, the largest asteroid in our solar system, and discover its remarkable ancient ocean and ice-rich crust.

A nearly new moon and mostly clear skies will present near ideal viewing conditions for the planet parade through Feb. 28.

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

Does our Solar System have 9 planets or only 8? Astronomers have gone back and forth on that a lot, with Pluto now being classified as a dwarf planet. However, out beyond Neptune there could be ...

Saturn, Venus, Neptune, Uranus, Jupiter, Mars and Mercury will be visible in an uncommon planetary alignment this month.

The dwarf planet is a bizarre ... a group of researchers led by the Max Planck Institute for Solar System Research (MPS) in Germany presents the most comprehensive analysis to date of this ...

Whether Pluto is officially a planet is the least interesting thing about the runt of the solar system, astronomers will tell you 95 years after the discovery of the fascinating and sometimes ...

In August 2006, the International Astronomical Union made the controversial, but correct, decision to demote Pluto from its ...