Jupiter-Mass Object Discovered Orbiting Brown Dwarf Challenges Planetary Definitions

In the CD-35 2722 star system, located 73 light-years from Earth, astronomers have discovered a Jupiter-mass entity orbiting a brown dwarf. This object, which is estimated to possess a mass of at least 0.9 times that of Jupiter, follows an elliptical path around the brown dwarf every 170 days. The brown dwarf itself orbits a smaller star, establishing a three-tiered system. Kevin Hoy, an astrophysicist from University Diego Portales in Chile, and his team refer to this entity as an 'exosatellite,' as it does not conform to the definitions of exoplanets or exomoons. Their research, published in Nature on July 22, utilized the Very Large Telescope in Chile from October 2023 to February 2026, yielding 23 observations. While some, like Nader Haghighipour from the Planetary Science Institute, view it as merely a brown dwarf, others, including Roman Rafikov from the University of Cambridge, see it as part of a binary system. Mary Anne Limbach from the University of Michigan supports the 'exosatellite' classification for such ambiguous objects, and Hoy embraces this ongoing discussion as a means to reevaluate astronomical terminology.