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Stolen Sedna

May 16, 2016

Our brilliant Sun may have a dark side: It may be a thief.

In particular, there’s evidence that it stole Sedna, a world more than twice as far from the Sun as Pluto is.

Sedna is much smaller than Pluto. But at the time of its discovery, in 2003, it was unique. That’s because, unlike Pluto and the other objects in the distant Kuiper Belt, it never approaches the paths of the giant planets, such as Neptune. That means that no giant planet’s gravity could have hurled Sedna from the inner solar system, where Pluto and similar objects are thought to have been born, into its remote orbit. Instead, the gravitational tugs of stars that were born with the Sun could have yanked Sedna outward.

In 2012, astronomers found another Kuiper Belt object that, like Sedna, never approaches the orbits of the giant planets. This discovery motivated them to investigate another idea: that the Sun stole Sedna from another solar system.

Computer simulations showed that the idea is plausible. They also revealed that the other star was more massive than the Sun, and that it passed quite close to the Sun.

If the Sun is a thief, both Sedna and the other object should come closest to the Sun on the same side of the Sun — and they do. But that could be just a coincidence. So astronomers hope to find more objects like Sedna. If they all come closest to the Sun on the same side of the Sun, then our home star probably is guilty of interstellar theft.


Script by Ken Croswell, Copyright 2015

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