Charon is the largest of Pluto’s five moons, with a radius more than half that of Pluto itself, but the question of how it came to orbit Pluto has puzzled astronomers. Read more Why the big bang ...

(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?

Because Charon couldn't sink into Pluto in this scenario, it remained beyond the so-called "co-rotation radius" of both bodies. As a result, it could not rotate as fast as Pluto, which meant the ...

Pluto, discovered in 1930, was once considered the ninth planet in our solar system. In 2006, the International Astronomical Union reclassified Pluto as a dwarf planet because it doesn't meet all ...