Fomalhaut b

Fomalhaut b, formally named Dagon (ˈdeigən), is a directly imaged extrasolar object and former candidate planet observed near the A-type main-sequence star Fomalhaut, approximately 25 light-years away in the constellation of Piscis Austrinus. The object's discovery was initially announced in 2008 and confirmed in 2012 via images taken with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope. Under the working hypothesis that the object was a planet, it was reported in January 2013 that it had a highly elliptical orbit with a period of 1,700 Earth years. The planetary hypothesis has since fallen out of favor; more recently gathered data suggests a dust or debris cloud is far more likely, and the most recent analysis places the object on an escape trajectory. The true nature of Fomalhaut b has been the subject of significant debate. Fomalhaut b was initially identified as one of the first exoplanets to be directly imaged: its detection was attributed to reflected light from circumplanetary material (e.g. a dust ring) and thermal emission from a jovian planet atmosphere. Later, Fomalhaut b was described as a low-mass planet which was only detected due to its surrounding dust cloud or, most recently, debris from a collision of asteroids instead. The object was one of those selected by the International Astronomical Union as part of NameExoWorlds, their public process for giving proper names to exoplanets. The process involved public nomination and voting for the new name. In December 2015, the IAU announced the winning name was Dagon. The name Dagon was proposed by Dr. Todd Vaccaro and forwarded by the St. Cloud State University Planetarium to the IAU for consideration. Dagon was a Semitic deity, often represented as half-man, half-fish. The most likely composition of Fomalhaut b is a dust cloud. Prior to 2020, a possible alternative was that Fomalhaut b could be a planet less than twice Jupiter's mass that is enshrouded in a spherical cloud of dust from ongoing planetesimal collisions.