Is Pluto a planet? What's up with the "space jellyfish?" And are aliens real? Astrophysicist, speaker and author Neil deGrasse Tyson, who is stopping in Pittsburgh later this month, answers our ...

Hundreds of people who love the little planet that was dissed, gather every year in the Arizona town where Pluto was discovered. They celebrate scientific discovery, history and our solar system’s ...

Add Yahoo as a preferred source to see more of our stories on Google. Once the quirky underdog of our solar system, Pluto held planetary status until 2006, when it got a cosmic demotion that still ...

Scientists who argue for Pluto to be classified as a planet are getting more ammo for a debate that has raged over the last 15 years. A team of researchers published a study in the scientific journal ...

Pluto will complete its first orbit since 1930 in 2178, a historic 248-year space journey that spans generations of humans.

(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 ...

Why does Pluto's orbit take so long? Pluto's orbit is not like those of the eight major planets, which are relatively circular. Instead, it is highly elliptical and tilted. At tim ...

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 ...