Have you ever wondered how long it takes for each planet to orbit the Sun? From Mercury’s blazing 88-day year to Neptune’s ...

Pluto hasn't been a planet for almost 20 years. In the early 2000s, scientists discovered several objects of a similar size to Pluto. So, during the summer of 2006, members of the International ...

Pluto’s thin, blue haze glows in this image from NASA’s New Horizons spacecraft. Though the dwarf planet is just a faint speck through a telescope, opposition this month offers skywatchers their best ...

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 the ...

Pluto, the king of the underworld, was the ancient Romans' embodiment of death itself. Known as Hades in Greek mythology, ...

(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? If ...