Exoplanet Astrometry
PALTA-1 b tugs a nearby ultracool dwarf
Eight years of Very Large Telescope astrometry reveal a candidate sub-Jupiter orbiting an L dwarf only about 17 parsecs away.
Briefed October 8, 2026 · Aliens in the Clouds
Accepted Study · Candidate Planet
Johannes Sahlmann and colleagues monitored the sky position of the early-L dwarf DENIS-P J1253108-570924 with the FORS2 instrument at the Very Large Telescope for more than eight years. Deviations from the star's expected proper motion and parallax yield the candidate planet PALTA-1 b, with an estimated mass between 0.54 and 0.77 Jupiter masses depending on the still-uncertain mass of its ultracool host.
The inferred system has a mass ratio near 0.010 and a relative separation of roughly 1.6 to 3.4 astronomical units. If confirmed, it would join a very small population of giant planets orbiting nearby ultracool dwarfs. The authors correctly retain the word ‘candidate’: the astrometric solution is compelling enough for an accepted paper, but independent follow-up is still needed to secure the planetary interpretation.
Why it matters
Giant planets around ultracool dwarfs test how efficiently low-mass disks can build massive companions, and astrometry reaches orbital separations that transit searches usually miss.
What the source establishes
Accepted Astronomy & Astrophysics manuscript submitted October 7. The positional wobble is measured; the companion mass range inherits uncertainty in the host's mass and the object remains explicitly classified as a candidate.
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