Discovered in 2008, the exoplanet Fomalhaut b, or Dagon, from the beginning, was acting strange: unlike other exoplanets, it was bright in the optical range and are virtually indistinguishable in the infrared. Scientists from the University of Arizona came to the conclusion that all this time we observed exoplanets, and the cloud of dust that formed due to the collision of two large bodies. Article published in PNAS.
The star Fomalhaut — alpha of southern Pisces, is at a distance of 25 light-years from the Solar system. In 2008, NASA announced that as a result of comparison of the images taken by the Hubble telescope in 2004 and 2006, visually proved the existence of a planet that revolves around a star. The existence of Fomalhaut b was questioned in 2010-2011, however, at the beginning of 2012 the complex of radio telescopes ALMA confirmed the presence of this object. In 2015, the international astronomical Union even awarded exoplanet own name — Dagon, in honor of the Semitic deity, the patron of fishing and rain.
Follow-up Dagon, however, raised the question about its planetary status. Unlike other exoplanets, Fomalhaut b was bright in the optical range and are indistinguishable in the infrared, and its orbit was crossed by a ring of asteroids around the star without the expected gravitational perturbations. Andras Gaspar (Gaspar Andras) and George Rieke (George H. Rieke) from the University of Arizona has revised the previously published observations, analyzed new data from the telescope “Hubble”, found that the exoplanet is on the “orbit of care”, which means that it is removed from the star. Moreover, Fomalhaut b faded and increased in size.
Astronomers have constructed a model of the expanding dust clouds resulting collision of large planetesimals and found that this model reproduces the light curve, angular size, and orbital motion that are consistent with observations of Dagon. What was a planet was a cloud of debris from the collision of two large bodies.
The authors note that similar phenomena in the planetary system of Fomalhaut age (he is about 300 million years) must be very rare. However, the number of such events should increase significantly if the hypothetical planet around a star are in the process of orbital migration.
Fomalhaut is not the only star around which discovered the so-called protoplanetary disk. N + 1 talked about how planets are formed in dust disks around stars.