Alpha Centauri Bb may be an ex-exoplanet. This long-sought world was announced with great excitement in 2012 as the first Earth-mass planet in the nearest star system to our own, but a new statistical analysis has revealed it to be nothing more than an apparition.
The original discovery was the work of Xavier Dumusque, then at the Geneva Observatory in Switzerland, and his colleagues. Using four years of data from the La Silla Observatory in Chile, they looked for a periodic wobble in the light from Alpha Centauri B, a star just 4.3 light years away.
After stripping out noisy contributions to the starlight, including star spots that can mimic transiting planets and the star’s own rotation, the team spotted a signal that seemed to repeat every 3.24 days. They attributed this to the gravity of a planet of that orbital period pulling on the star.
Since then, other astronomers had tried other methods of filtering out the star’s noisy signal, and found that the evidence for planet Bb was inconclusive. But they couldn’t rule it out.
“Most people have been focusing their attention on trying to model the stellar activity,” says Vinesh Rajpaul of the University of Oxford. But now he and his colleagues have discovered that the signal could have been introduced by the way the measurements were made.
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