So the newfound objects either orbit a star more distant than that, or they don't orbit a star at all, the researchers concluded. They drew on other data to determine most of the objects don't orbit a star.
Scientists believe planets are formed when disks of dust that orbit stars form clumps, so that these clumps — the planets — remain in orbit. Maybe the newfound objects started out that way, but then got tossed out of orbit or into distant orbits by the gravitational tugs of larger planets, the researchers suggest. The work suggests that such a tossing-out process is quite common, Bennett said.
Boss said maybe the bodies formed around a pair of stars instead, one of which supplied the gravitational tug. But even that would take some explaining to produce an object without an orbit, he said. Or maybe they somehow formed outside of any orbit. So the theoretical challenge in explaining the existence of such bodies is "exciting," he said. Boss said he suspects most of these are in a distant orbit, and that maybe they even formed at that great distance rather than being tossed outward from a closer orbit.
Kaltenegger also said the new results can't rule out the possibility that these possible planets are in orbit, and that they may only have the mass of Saturn, about a third of Jupiter's.
But if they aren't orbiting a star, she noted, they don't fit the official definition of a planet — at least not the definition applied to objects in our own solar system. All in all, Boss said, the new work is "pretty exciting in telling what is out there in the night sky... Lots of theories will grow in this environment."
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