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Revealing Fomalhaut b's True Nature

Assistant Astronomer Andras Gaspar and Professor George Rieke propose a solution to the decade old mystery of the first directly imaged exoplanet, Fomalhaut b, in an article recently published in the Publications of the National Academy of Sciences. First discovered in 2008 in images taken with the Hubble Space Telescope (HST) in 2004 and 2006, Fomalhaut b has always been an enigmatic object within the group of roughly two dozen directly imaged exoplanets. Despite being observed multiple times in the optical, it remains undetected at infrared wavelengths, contrary to expectations for a massive planet. In addition, its eccentric orbit crosses the debris ring around the star, yet the ring does not show the perturbations expected from interaction with a massive planet. 

 
While designing upcoming observations of the Fomalhaut debris disk system using their group's Guaranteed Observing Time on the James Webb Space Telescope, Gaspar methodically reduced all archival HST observations on the system, including unpublished 2013 and 2014 data. To his surprise, the Fomalhaut b object was not detected in the 2014 dataset, leading to their in-depth analysis and theoretical modeling of the Fomalhaut b object. 


Additionally, they found that the object has been fading since its first observation and that its size (spatially resolved in the later datasets) has been increasing. Finally, its orbit was now better explained by an escaping trajectory. These observational aspects all pointed towards a single plausible explanation: the object is a large expanding dust cloud on a radially escaping path. Such a cloud would be produced by a massive collision between two large asteroidal objects.
 
Dr. Gaspar gave us three photos: HERE is a video of the system over time. 
HERE is the cover photo. And HERE is an artist's conception of creating the dust cloud. 

 

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