Neptune Might Have Captured Triton

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Neptune Might Have Captured Triton
An artist's conception of Triton and its binary companion as they approach Neptune. This encounter facilitated Triton’s capture to an inclined retrograde orbit around Neptune, an event that catastrophically altered the Neptune satellite system. (Image credit: Craig Agnor)

Neptune's largest moon, Triton, was originally a member of a duo orbiting the Sun but was kidnapped during a close encounter with Neptune, a new model suggests.

Triton is unique among large moons in that it orbits Neptune in a direction opposite to the planet's rotation, which long ago led scientists to speculate that the moon originally orbited the Sun. But until now, no convincing theory for how Triton paired with Neptune existed.

"We've found a likely solution to the long-standing problem of how Triton arrived in its peculiar orbit," said Craig Agnor, a researcher from the University of California, Santa Cruz. "In addition, this mechanism introduces a new pathway for the capture of satellites by planets that may be relevant to other objects in the solar system."

The new model predicts that Triton came from a binary setup much like Pluto and its moon, Charon. 

"It's not so much that Charon orbits Pluto, but rather both move around their mutual center of mass, which lies between the two objects," Agnor said.

Sara Goudarzi
Sara Goudarzi
Sara Goudarzi is a Brooklyn writer and poet and covers all that piques her curiosity, from cosmology to climate change to the intersection of art and science. Sara holds an M.A. from New York University, Arthur L. Carter Journalism Institute, and an M.S. from Rutgers University. She teaches writing at NYU and is at work on a first novel in which literature is garnished with science.