(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?

ammonia-bearing species and organic materials responsible for its gray and red coloration." Related: Pluto's huge white ...

Pluto, with its heart-shaped glacier, as captured by the New Horizons spacecraftJPL/NASA Pluto will mark a birthday of sorts on March 23, 2178. No one is likely to be there to celebrate it, of ...

Pluto was discovered at Lowell Observatory in Flagstaff, Arizona in 1930 and was considered our ninth planet until 2006. The International Astronomical Union reclassified Pluto as a dwarf planet ...

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 ...

Pluto is too far away from Earth to be seen with the naked eye. If you stood on Pluto's surface, the Sun would merely appear to be a very bright star. Although previous images showed that ...