Growing up, I was taught that there were nine planets in the solar system. That all changed in 2006, when the International Astronomical Union voted to demote Pluto's status to that of dwarf planet.

This once-in-a-generation shift is a pivotal power play in a saga that will unfold in the years and decades to come.

A powerful new tool comes online this year that could help astronomers locate the mysterious planet hiding somewhere beyond ...

it has flown for nine and a half years to the outer edges of the solar system . . . SLIDESHOW: NASA’s New Horizons Mission . . . to Pluto, the now-demoted “dwarf planet” that lives beyond ...

Although Seeing in the Dark doesn't directly discuss Pluto, it does celebrate the joy of observing planets. Viewers who watch the show may wonder what happened to Pluto in 2006 and whether any of ...

Rumya Sundaram, Citizen Scientist Coordinator for the Key Biscayne Community Foundation, will present this month’s Citizen ...

Aside from the solar system once again having nine planets—which it had before Pluto’s demotion in 2006—the discovery of a distant Earth-mass planet would have profound implications for ...

Rachel Feltman: For Scientific American’s Science Quickly, I’m Rachel Feltman. Unless you’re really on the low end of our listener age bell curve, chances are you grew up learning about our ...

NASA launched the New Horizons probe which would provide never-before-seen images of the dwarf planet, its moons and other objects.