Team Detects 0.9-Jupiter Exomoon Candidate Orbiting Brown Dwarf 73 Light-Years Away
Updated
Updated · WIRED · Aug 1
Team Detects 0.9-Jupiter Exomoon Candidate Orbiting Brown Dwarf 73 Light-Years Away
3 articles · Updated · WIRED · Aug 1
Summary
A 0.9-Jupiter-mass moonlike body appears to orbit brown dwarf CD-35 2722 B every roughly 170 days, offering what researchers call the first evidence of an exosatellite beyond the solar system.
Twenty-three nights of VLT CRIRES+ observations from October 2023 to February 2026 tracked the brown dwarf’s Doppler wobble, with measurements up to 100 times more precise than earlier attempts.
The signal survived checks for Earth-motion correction errors, seasonal atmospheric effects and the brown dwarf’s rotation, while Roche-limit and Hill-radius calculations indicated the orbit is physically stable.
CD-35 2722 B is about 37 times Jupiter’s mass, making the companion about 2.5% of its mass—larger by ratio than any planet-moon pair in the solar system, including Earth-Moon at about 1.2%.
Researchers say the find blurs the line between moon, planet and star because no formal exomoon definition exists, but it could reshape formation theories and guide future searches with the 39-meter Extremely Large Telescope.