Back in the 1980’s, a now-defunct magazine called Science Digest held a contest to name Planet X — the still-undiscovered world that astronomers believed might lie out beyond Pluto. One of the best ...

Pluto may have been demoted to non-planet status, but it still commands a court of five moons, as is fitting for the king of darkness; after all, Pluto is the Roman equivalent of the Greek God Hades.

This composite image of Pluto, right, and Charon, its largest moon, showcases photos captured by NASA’s New Horizons spacecraft in July 2015. Unlike how scientists believe Earth's moon formed billions ...

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