Our solar system鈥檚 first interstellar visitor may be a shard of a larger planet that got shredded by its star.
Astronomers spotted a strange, fast-moving object in October that seems to be an interloper from beyond our solar system. Named 鈥極umuamua, it seems to be a cigar-shaped rock that tumbled into our neighbourhood from around another star.
Now, researchers are trying to figure out where 鈥極umuamua came from and how it formed. at the SETI Institute thinks it may have been born when a planet about 10 times the size of Earth got too close to its small, dense star and was shredded to bits. The debris could have been punted away by the gravitational tug of a second orbiting star.
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If 鈥極umuamua is typical of the population of rocks that travel from star to star, and it鈥檚 not the only one out there, Cuk says this origin story could account for most of them.
Remnants of doom
Cosmic collisions are not likely to create elongated objects, Cuk suggests. When two objects violently smash into each other in space, the resulting debris often continues to crash together. A long, thin rock like 鈥極umuamua would likely crack down the middle in such violent conditions.
Instead, he says, if a planet about 10 times the size of Earth is torn apart by a dwarf star and the resulting fragments shoot out of the system, many objects like 鈥極umuamua could be created at once.
鈥淚n order to figure out what 鈥極umuamua really is, we need to find at least a few more interstellar objects,鈥� says at Queen鈥檚 University Belfast. There are several other theories for how space rocks like this can form, and few of them can be definitively ruled out without more observations. But planets and stars of the necessary sizes are abundant in the universe, so Bannister says that this idea is certainly plausible.
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Read more: We got a good look at the interstellar asteroid and it鈥檚 weird
