![Planet mass as a function of host mass for systems included in the NASA Exoplanet Archive (Christiansen et al. 2025) queried on 4 March 2026. Only systems with a host mass M < 0.2 M⊙ and available system distance are shown. PALTA-1 b is indicated with a diamond and the symbol colour indicates the system’s distance from the Sun.-- [astro-ph.EP]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/10/Astrometric-planet.png?fit=1200%2C676&ssl=1)
[astro-ph.EP] We report the discovery of PALTA-1 b, a sub-Jupiter mass exoplanet candidate orbiting the nearby early-L dwarf DENIS-P J1253108-570924 (DE1253-57) located at a distance of ~17 pc.
The exoplanet was discovered by monitoring the L dwarf’s astrometric motion with FORS2 at the Very Large Telescope over more than eight years and characterising the deviations from the expected single-source motion.
The estimated planet mass is between 0.54 MJup and 0.77 MJup, depending on the uncertain mass of the ultracool dwarf 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 the very few known examples of a giant planet orbiting a nearby ultracool dwarf. This discovery finalises a larger astrometric planet search survey that targeted 20 nearby ultracool dwarfs and previously discovered three new ultracool binary systems.
J. Sahlmann, P. F. Lazorenko, E. L. Martín, D. Ségransan, M. Mayor, S. Udry
Comments: 12 pages, 10 figures. Accepted for publication in A&A
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2610.09965 [astro-ph.EP] (or arXiv:2610.09965v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2610.09965
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Submission history
From: Johannes Sahlmann
[v1] Wed, 7 Oct 2026 12:36:53 UTC (330 KB)
https://arxiv.org/abs/2610.09965
Astrobiology, exoplanet,
