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New Analyses Resurrect Contested Exoplanet Claim

Fomalhaut b looked like an exoplanet to some astronomers and like dust to others. But new analyses strengthen the planet view. John Matson reports

Seeing is believing. And then disbelieving. And maybe believing once more.

The exoplanet Fomalhaut b was the first one photographed with visible light. Researchers using the Hubble Space Telescope spotted it in 2008, orbiting a star 25 light-years away. The sighting made big news, because almost all exoplanet discoveries before or since were indirect detections. But with Fomalhaut b, astronomers could actually see the planet.

Well, some astronomers. Researchers using the Spitzer Space Telescope could not see Fomalhaut b at all in infrared light. They concluded that what Hubble had seen was probably just a transient dust cloud.

Now two new studies posted at arxiv.org have strengthened the planetary argument. Two teams reanalyzed the data and confirmed that there is something there. But what? One group concluded that the object could be the debris from a smashup of two small objects, or it could be a planet surrounded by a disk of dust. [Raphaël Galicher et al, Fomalhaut b: Independent Analysis of the Hubble Space Telescope Public Archive Data] The other group favors the hypothesis that Fomalhaut b is an exoplanet, albeit one shrouded in dust. [Thayne Currie et al, Direct Imaging Confirmation and Characterization of a Dust-Enshrouded Candidate Exoplanet Orbiting Fomalhaut]

Paul Kalas, one of the planet’s original discoverers, says he will have new data to show in January. Until then, it’s either Fomalhaut or Fomal-naught.

—John Matson

[The above text is a transcript of this podcast.]

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