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

“New Horizons shattered a major paradigm of planetary science,” says Alan Stern, the mission’s principal investigator. “Pluto ...

On the 95th anniversary of its discovery, Pluto remains one of the most beloved and enigmatic worlds in our solar system, ...

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

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 ...

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

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

An amateur astronomer discovered Pluto 95 years ago today. The former planet will complete an orbit in another 153 years.

It did have five known moons: Charon, Nix ... Union General Assembly adopted a resolution to reclassify Pluto as a dwarf planet. The reasoning was that it didn't satisfy one of three newly ...

That, plus Pluto’s small size—smaller than our moon—suggested that the ... solar system with an uncounted number of planets. Stern thinks the dwarf planet distinction is nonsensical ...

He called this hypothetical world "Planet X." "In some ways, Pluto's more of a planet than some of the other established planets, like Mercury." ...