VLT astrometry finds sub-Jupiter planet candidate around nearby L dwarf
Eight years of Very Large Telescope monitoring point to a giant planet candidate around a nearby L dwarf.
Astronomers have reported PALTA-1 b, a sub-Jupiter mass exoplanet candidate orbiting the early-L dwarf DENIS-P J1253108-570924, which lies about 17 parsecs away. The paper, led by J. Sahlmann with five co-authors, was submitted to arXiv on 7 October 2026.
The team found the planet by tracking the L dwarf's astrometric motion with the FORS2 instrument at the Very Large Telescope for more than eight years. They then characterised deviations from the motion expected of a single source.
The estimated planet mass is between 0.54 and 0.77 Jupiter masses, depending on the uncertain mass of the host. The system's mass ratio is about 0.010 and the relative separation is estimated at 1.6-3.4 au.
If confirmed, PALTA-1 b would be one of very few known giant planets orbiting a nearby ultracool dwarf. The result completes a survey of 20 nearby ultracool dwarfs, which had previously turned up three new ultracool binary systems.
Sourcearxiv.org