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

"The data from the termination shock encounter will be a treasure trove for space physicists worldwide who are eager to ...

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." ...

They did, and the discovery of Planet X was announced on March 13, 1930. An 11-year-old English schoolgirl, Venetia Burney, suggested the name Pluto, the god of the underworld. Tombaugh’s ...

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 ...