A Moment of Science

Sedna

Learn about the most distant object to orbit the sun, on this Moment of Science.

Pluto is the last of the nine planets, and when it’s at its farthest point in its elliptical orbit, it’s the farthest planet from the sun. However, it is not the farthest object from the sun.

Discovered recently, Sedna is a super-distant object orbiting the sun. It’s even further out than Pluto! It’s been dubbed a “planetoid”–think of it as a mini-planet, three quarters as big as Pluto. It’s smaller than our moon. But Sedna may have a moon of its own, and if it were a lot closer, we might have called it a planet long ago.

Sadly for Sedna, it’s way out there–about eight billion miles away. That’s a whopping three times farther from the sun than even Pluto is. Sedna is so distant, and tiny, that it was only discovered for the first time this year by astronomers at the California Institute of Technology in Pasadena.

Sedna is already fascinating folks, though, because it is very reflective and reddish colored, confusing astronomers as to what it might be made of. It also has a bizarrely elongated orbit, going around the sun only once every ten thousand years!

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