TESS discovers a rare brown dwarf orbiting a massive, aging star
For decades, astronomers lumped brown dwarfs into a single category defined by mass alone—too big to be classified as planets but too small to become stars. However, this definition ignores the two very different mechanisms that can form them: the direct collapse of gas clouds and formation within the accretion disks of massive stars.
Astronomers have identified a brown dwarf, designated HIP 61637 b, orbiting a massive, aging star through observations from NASA's Transiting Exoplanet Survey Satellite (TESS). Brown dwarfs, which are more massive than planets but not quite stars, have been traditionally classified based solely on their mass. However, recent analysis reveals that there are two distinct methods of brown dwarf formation: direct gas cloud collapse and formation within accretion disks of massive stars.
The discovery of HIP 61637 b in orbit around an aging A-type star nearly three times the mass of the Sun provides new insights into how these planet-like bodies form. The system's age has been determined with high precision, making HIP 61637 b one of just seven brown dwarfs with a known age. The brown dwarf's 48 Jupiter mass size suggests it may have formed through gradual disk accretion, although its mass challenges the established formation limits.
This rare observation contributes to the understanding of transiting brown dwarfs with well-defined ages, potentially clarifying whether these objects are failed stars, overgrown planets, or something else entirely.
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