planet
December 6, 2015

How accurate is Kepler? Study calls the space observatory into question

The Kepler space observatory, which orbits the sun and collects data on stars in search of potential Earth-like planets, has identified 8,826 objects of interest, with 4,696 being considered possible planets and 1,030 being confirmed, according to CNET.

Now, a study awaiting publication in the journal Astronomy and Astrophysics has found that while it was previously thought that Kepler’s giant exoplanet detection was fairly accurate with a margin of error of between ten and twenty percent, it turns out that it’s much higher—half or more of the detected planets are probably not actually planets at all, according to the study.

"It was thought that the reliability of the Kepler exoplanets detection was very good—between 10 and 20 percent of them were not planets," said Alexandre Santerne from Portugal’s Institute of Astrophysics and Space Sciences in a statement. "Our extensive spectroscopic survey, of the largest exoplanets discovered by Kepler, shows that this percentage is much higher, even above 50 percent. This has strong implications in our understanding of the exoplanet population in the Kepler field."

It turns out, 52.3% of possible planets are actually just eclipsing binary stars, according to the source—pairs of stars that orbit each other. Planets are detected based on the subtle movements and light dimming of stars, so two stars influencing each other’s behavior can be a real headache planetary researchers.

Vardan Adibekyan, a team member on the study, said, "Detecting and characterizing planets is usually a very subtle and difficult task. In this work, we showed that even big, easy-to-detect planets are also difficult to deal with. In particular, it was shown that less than half of the detected big transiting planet candidates are actually there. The rest are false positives, due to different kinds of astrophysical light sources or noise."

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Image credit: NASA JPL