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A dwarf planet far from the Sun may spend most of its time outside the Sun’s influence. In fact, it might have come from interstellar space – from another star.

Sedna takes more than 11,000 years to orbit the Sun. It’s passing through the Kuiper Belt – a wide “doughnut” far beyond the orbit of Neptune, the Sun’s most distant major planet. Right now, Sedna’s almost eight billion miles from the Sun – about as close as it ever gets. At its most distant, it’s more than 10 times farther. That places it far beyond the Kuiper Belt – and well outside the “bubble” produced by the Sun’s magnetic field.

Scientists have speculated that Sedna started in the Oort Cloud – a big “shell” of rocky, icy bodies that surrounds the Sun. It could have been pushed into its elongated orbit by the gravity of a passing star. Or it could have been a member of another star system that was pulled away by the Sun.

There’s one other oddity about Sedna’s orbit: It seems to be influenced by the gravity of a much larger but unseen body far from the Sun – a possible “Planet Nine.”

Because Sedna’s so far away, we don’t know a lot about it. It’s probably about 600 miles in diameter. And it’s quite red – an indication that radiation has been zapping its surface for a long, long time. No one has found a moon yet, so it’s hard to measure Sedna’s mass. So we still have a lot to learn about this remote little world far, far from the Sun.

Script by Damond Benningfield

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