Three 'known' Kepler exoplanets are more likely to be stars

They're simply too big to be planets.

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The hunt for exoplanets has apparently led to a few near misses. MIT researchers have discovered that three "planets" observed using the Kepler Space Telescope (Kepler-699b, Kepler-840b and Kepler-854b) are more likely to be small stars. They're simply too big, the scientists found — at two to four times Jupiter's size, they're larger than the largest confirmed planets.

A fourth, Kepler-747b, might also be ruled out. It's small enough ('just' 1.8 times Jupiter's size) to be a planet, but it's distant enough that it doesn't receive enough light to be sustainable. It's "not entirely implausible" that 747b is a planet, according to MIT, but you won't want to make any bets.

The team found the discrepancies after obtaining improved measurements from the European Space Agency's Gaia observatory and double-checking the original classifications. Astronomers were only looking for tidal distortion at first, but noticed odd ellipsoidal signals (the ellipsoid shapes that hint at gravitational pull) that were too large for planets.

MIT doesn't expect many more false planets. This is a "tiny correction," the school's Avi Shporer said. As it stands, this refinement is just what the scientists want — it produces more reliable data that should help with other, broader exoplanet studies.