More than half Kepler planet candidates false positives

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The uncertainty of science: In attempting to confirm the giant exoplanet candidates in the Kepler telescope database a team of scientists has found that more than half are not planets at all but false positives.

An international team1 led by Alexandre Santerne from Instituto de Astrofísica e Ciências do Espaço (IA), made a 5-year radial velocity campaign of Kepler’s giant exoplanet candidates, using the SOPHIE spectrograph (Observatory of Haute-Provence, France), and found that 52,3% were actually eclipsing binaries, while 2,3% were brown dwarfs. Santerne (IA & University of Porto), first author of this paper commented: “It was thought that the reliability of the Kepler exoplanets detection was very good – between 10 and 20% of them were not planets. Our extensive spectroscopic survey, of the largest exoplanets discovered by Kepler, shows that this percentage is much higher, even above 50%.

The news article above is unclear about the number of candidates total this study actually looked at and pinned down. It appears they began looking at the full database of almost 9,000 candidates, but then narrowed it to 125. Were 50% of the 9,000 false positives, or of the 125? The article is unclear.

At first glance, this study appears to tell us that there might be fewer giant Jupiter-sized exoplanets out there than previously thought. Then again, the data is uncertain enough that this conclusion could easily be wrong. The real take-away is that the science of exoplanets has only just begun, and that sweeping generalizations about the nature of solar systems in the galaxy are exceedingly unreliable. We simply don’t know enough yet.


  • MikeP

    Just think of the brown dwarfs and smaller stars in the binary systems as luminous planets and the uncertainty goes away.

  • Really? Your research capabilities amaze me. I suppose we can now abandon any further research effort, because you have explained everything astronomers are so unsure of, and thus have no need to waste our time trying to figure things out. MikeP knows, and can explain all!

  • MikeP

    Robert, I am not saying anything that they aren’t saying. They state that it is binary systems and binary systems including brown dwarfs that are causing “false positives” for planets. The “planets” in that half of the sample are thus orbiting stars. You could view such orbiting stars, in a sense, as luminous planets.

  • PeterF

    Perhaps it would be more useful to describe Kepler as successful in detecting eclipsing events but that those events were not necessarily planetary in origin. This is the reason that astronomers need to verify the cause of the eclipsing event. Only after verification by an alternate sensor can “dual phenomenology” be cited as reasonable certainty that an exoplanetary system has been identified.
    Also remember that Kepler is useful only in detecting systems whose orbital plane aligns with our system. Frankly, I am surprised that they have found as many candidates as they have. (If you lived on Pluto, how long would you have to observe the sun before you observed any planet other than Mercury eclipsing the sun?) multiply that by (a billion?, a trillion?) to calculate the length of time required to observe a neighboring star to get even a glimpse of a transit of a planet orbiting at one AU.

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