The case of the vanishing exoplanet
In 2008, astronomers using the Hubble Space Telescope announced the discovery of an exoplanet orbiting the star Fomalhaut a scant 25 light years away. First seen in 2004 and again in 2006, the presumed planet – Fomalhaut b – was brighter than would normally be expected and appeared to be following an unusual trajectory just inside a vast cloud of icy debris orbiting the star. Then, in 2014, astronomers were stunned to find Fomalhaut b had disappeared. A search through archived data revealed it had slowly faded from view over several years. Astronomers now think Fomalhaut b was never a fully evolved planet in the first place. Instead, the data suggest the bright object Hubble originally spotted was, in fact, a huge cloud of expanding dust in the aftermath of a collision between two asteroid-size bodies. Gáspár, George Rieke of the University of Arizona’s Steward Observatory and a team of collaborators believe the apparent collision occurred shortly before the first images of Fomalhaut b were collected in 2004. By 2014, the object had disappeared from view after fading over several years. Along with its slow fading, Fomalhaut b is likely on an escape trajectory, not in a planet-like elliptical orbit, a natural result of the host star’s influence on a massive, expanding dust cloud.