Exoplanet candidate PALTA-1 b found orbiting a nearby ultracool dwarf

Researchers have identified a new exoplanet candidate, PALTA-1 b, orbiting an ultracool dwarf star located approximately 55 light-years away. By monitoring the star's precise position over eight years, the team detected subtle wobbles indicating the presence of a sub-Jupiter mass companion. This finding adds to the rare population of giant planets discovered around small, low-temperature stars.

Star system: DENIS J1253-5709 | Distance from the Sun: 54.4 light years

An exoplanet candidate named PALTA-1 b has been identified orbiting the ultracool dwarf star DENIS-P J1253108-570924. This star is classified as an early-L dwarf, a type of extremely cool and small star that occupies the boundary between the lowest-mass stars and brown dwarfs. Located about 55 light-years from our solar system, this system provides a rare opportunity to study how giant planets form and evolve around such low-mass stellar hosts.

The discovery relied on astrometry, a technique used to measure the precise position and movement of stars in the sky. By using the FORS2 instrument on the Very Large Telescope, the team tracked the star's path for more than eight years. They looked for minute deviations from a perfectly straight path, which are telltale signs that the gravitational pull of an orbiting planet is causing the star to wobble. These tiny shifts in position allowed the team to calculate the presence and characteristics of the planet.

Calculations suggest that PALTA-1 b has a mass between 0.54 and 0.77 times that of Jupiter, depending on the exact mass of the host star. The planet maintains an estimated distance from its host star of 1.6 to 3.4 astronomical units, which is the average distance between the Earth and the Sun. This finding concludes a long-term survey that monitored 20 nearby ultracool dwarfs, reinforcing the rarity of giant gas planets in these environments.

Key findings
PALTA-1 b is a sub-Jupiter mass exoplanet candidate orbiting an ultracool dwarf.
The system has a mass ratio of approximately 0.010 between the planet and the host star.
The estimated separation between the planet and its star is 1.6 to 3.4 astronomical units.
The discovery follows eight years of precise astrometric monitoring at the Very Large Telescope.

Scientific study

Astrometric planet search around southern ultracool dwarfs: V. Discovery of the exoplanet candidate PALTA-1 b (external link)