Kepler Planets Turn Out to be Small Stars

Using new data from ESA’s Gaia observatory, researchers recalculated the masses of several different exoplanets and found three are likely stars instead.

IMAGE: Among thousands of known exoplanets, MIT astronomers have flagged three that are actually stars. Pictured is an artist’s interpretation of stars and planets. CREDIT: NASA

A new study published in The Astronomical Journal reports that three and maybe even four objects originally classified as exoplanets in Kepler data are actually small stars. Oops.

The research team behind this paper used updated measurement techniques and discovered that Kepler-854b, Kepler-840b, and Kepler-699b are about two to four times the size of Jupiter. This makes them too big to be planets, at least so far as we have been able to confirm when it comes to exoplanets. First author and graduate student Prajwal Niraula explains: Most exoplanets are Jupiter-sized or much smaller. Twice [the size of] Jupiter is already suspicious. Larger than that cannot be a planet, which is what we found.

That’s where that possible fourth star-not-planet comes in. Kepler-747b is only about 1.8 times the size of Jupiter, which sets it right on the cusp of being too big to be an exoplanet. However, a more detailed look at the object finds that it is relatively distant from its star, so it doesn’t get enough light to be that big a planet. But there are some other confirmed exoplanets…