[Slashdot] - Scientists Believe 'Oumuamua Was Chunk of Extrasolar Pluto-Like Planet

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lazarus shares a report from Phys.org: Two Arizona State University astrophysicists, Steven Desch and Alan Jackson of the School of Earth and Space Exploration, set out toexplain the odd features of 'Oumuamua and have determined that it is likely a piece of a Pluto-like planet from another solar system. Desch and Jackson hypothesized that the object was made of different ices and calculated how quickly these ices would sublimate (passing from a solid to a gas) as 'Oumuamua passed by the sun. From there, they calculated the rocket effect, the object's mass and shape, and the reflectivity of the ices. The scientists found one ice in particular -- solid nitrogen -- that provided an exact match to all the object's features simultaneously. And since solid nitrogen ice can be seen on the surface of Pluto, it is possible that a comet-like object could be made of the same material. "We knew we had hit on the right idea when we completed the calculation for what albedo (how reflective the body is) would make the motion of 'Oumuamua match the observations," said Jackson, who is a research scientist and an Exploration Fellow at ASU. "That value came out as being the same as we observe on the surface of Pluto or Triton, bodies covered in nitrogen ice." They then calculated the rate at which chunks of solid nitrogen ice would have been knocked off the surfaces of Pluto and similar bodies early in our solar system's history. And they calculated the probability that chunks of solid nitrogen ice from other solar systems would reach ours. "It was likely knocked off the surface by an impact about half a billion years ago and thrown out of its parent system," Jackson said. "Being made of frozen nitrogen also explains the unusual shape of 'Oumuamua. As the outer layers of nitrogen ice evaporated, the shape of the body would have become progressively more flattened, just like a bar of soap does as the outer layers get rubbed off through use."

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