If you answered "Pluto's planethood," your grasp of the astronomical is excellent. Feb. 18 marks the 95th anniversary of the discovery of our outermost planet-not-planet. Here's what to know about ...

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." ...

keeping the gases in Pluto’s upper atmosphere cool so that molecules no longer have enough energy to escape the dwarf planet. Without this hazy atmosphere, Pluto’s volatile glaciers would have ...

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 ...

Therefore, the IAU says Pluto can't sit at the cool kids table with Venus and Saturn; its proper place is with bitch-ass dwarf planets like Quaoar, Sedna, and Orcus. Pluto's demotion was partially ...

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 ...

The planets you should be able to spot without a telescope on Friday, include Mercury, Venus, Jupiter, and Mars. Do you have ...

Venus, Mars, Jupiter, Saturn, Uranus, and Neptune were already visible in the night sky after dusk this month, but Mercury joined them on Feb. 28. While it's common to see a few planets line up in the ...

Prague, CZECH REPUBLIC: Members of the International Astronomic Union (IAU), vote on the Resolution for Planet Definition 24 August 2006 in Prague. The resolution demoted Pluto from its status as ...