Absent without leave
Aaron Loose discusses the disappearing trick performed by the planet Fomalhaut B
Usually, planets don’t simply disappear. But Fomalhaut B, an exoplanet that was first photographed in 2004, seems to have pulled off a celestial vanishing act like no other.
Despite being visible during several years of Hubble observations, the object disappeared from the Hubble telescope’s vision entirely in 2014.
“Fomalhaut B… seems to have pulled off a celestial vanishing act like no other”
However, according to a recent article published in Science Daily, there is a convincing explanation for the wandering star’s magic trick. In fact, new research suggests Fomalhaut B might not be a planet at all. Rather, it could be a ginormous cloud of dust created by a collision between two large planetary objects. The interpretation is still unconfirmed, but if true, the conclusion offers a new insight into the humbling ways in which stars eradicate one another.
Fomalhaut B has always behaved erratically. As an exoplanet – an extrasolar object outside of our home solar system – it is already difficult to detect. The existence of such exoplanets is often deduced indirectly from the subtle shadows cast by planetary bodies passing in front of a star.
Yet Fomalhault B was especially elusive. Located over 25 light years from Earth in the distant Fomalhaut system, the object was unusually bright yet gave no infrared heat signature. Stranger still, earlier images indicated the object was gradually fading over time.
“Images indicated the object was gradually fading over time”
Scientists András Gáspár and George Rieke, both of the University of Arizona, think Fomalhaut B was never an exoplanet, but was an expanding cloud of dust. The crash that formed it might have happened a little time before the first photographs were taken in 2004.
Today, the resulting dust cloud is estimated to have grown to a size larger than the orbit of Earth around the sun. In astronomer’s parlance, dust does not mean dirt, but refers to fine grains of carbon and ice.
Complex dust computer modelling at the University of Arizona indicates that the dust cloud interpretation is supported by all information currently available about Fomalhaut B.
Gáspár and Rieke will continue to observe the Fomalhaut system, wherein the team shall search for orbiting planets that may be gravitationally shaping the system’s outer disk.