A new study finds that more than half of the gas giant planets candidates in the NASA’s Kepler data are false positives — aren’t planets at all — a rate much higher than previously thought.
The team of astronomers, led by Alexandre Santerne, tracked 8,826 Kepler objects of interest (KOI), exoplanets discovered by Kepler using a ground-based telescope over a period of five years. Then they narrowed the number down to 129 objects on 125 target stars by removing false positives. It turns out, 52.3% of the possible objects are actually just eclipsing binary stars, while another 2% were found to be brown dwarfs.
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 Santerne ~ study lead author.
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.
Santerne and his colleagues used the SOPHIE spectrograph, an instrument installed on a telescope at the Observatory of Haute-Provence in France, to check Kepler’s candidate, world that thought to be large gas giant planets — like Jupiter or Saturn — or even larger.
The SOPHIE is a spectrograph capable of observing and measuring the dimming of starlight produced by the gravitational pull as an exoplanet crosses in front of its host star, like a mini-eclipse. This method, known as the radial velocity method, is used to determine the mass of the orbiting objects.
Detecting and characterizing planets is usually a very subtle and difficult task,
researcher Vardan Adibekyan said.
In this work, we showed that even big, easy to detect planets are also difficult to deal with. In particular, it was showed that less than half of the detected big transiting planet candidates are actually there. The rest are false positives, due to different kind of astrophysical sources of light or noise.
So, Santerne’ result mean that there are fewer planets out there than we previously thought? Not really, researchers said.
It’s “really nice work” but that the implication that half of all Kepler candidates are actually false positives is misleading. The new study applies only to giant planet candidates; the false-positive rate drops significantly with smaller worlds, such as those the size of Earth
Jeff Coughlin said.
It’s much easier to have an eclipsing binary mimic a very large planet,” he said. “It’s hard to get it to mimic a very small planet.
I think at least 80 percent is a good number,
he said, referring to the percentage of Kepler candidates that should eventually be confirmed.
Note: NASA’s Kepler space observatory has been orbiting around the sun since 2009, collecting data on 150,000 stars, all while searching for Earth-like planets in the Milky Way galaxy. Of the total 8,000-plus objects of interest, 4,696 are planet candidates, of which more than 1,000 have been confirmed as planets. Twelve of those have been confirmed as existing in habitable zones. ~ reported rt.com.