Pluto will mark a birthday of sorts on March 23, 2178. No one is likely to be there to celebrate it, of course. Even if ...

The revelation that Pluto and its large moon may have collided, causing Pluto to be geologically active, could mean there are ...

Pluto never really fit in with the other planets in the solar system. Its orbit was out of plane with the other planets. From 1979 to 1999, it was closer to the sun than Neptune. When other bodies ...

(Correction: An earlier version of this story misstated how far Pluto is from the sun. The correct number is 3.7 billion miles.) What was discovered in Flagstaff, Arizona, and killed off in Prague?