Using data from TRAPPIST-South/North, SPECULOOS, and MuSCAT3 facilities, astronomers have discovered an unusual Jupiter-sized exoplanet orbiting the red dwarf TOI-4860.
An artist’s impression of a gas-giant exoplanet. Image credit: Sci.News.
TOI-4860 resides at a distance of 80 parsecs (261 light-years) in the constellation of Corvus.
Also known as 2MASS J12141555-1310290, TIC 335590096, or Gaia DR2 3571038605366263424, this red dwarf of M4.5 type (a star at the transition between fully and partially convective interiors) has a mass of 0.34 solar masses.
The newfound planet is unusual for two reasons: stars of such low mass are not expected to host planets like Jupiter, and the planet appears to be particularly enriched by heavy elements.
Named TOI-4860b, the planet has a radius of 0.76 Jupiter radii and takes about 1.52 days to complete a full orbit around the star.
Because its host is a cold low mass star, the planet itself can be referred to as a warm Jupiter.
This is a subclass of planet that holds particular interest for astronomers looking to build on their initial observations and learn more about how these kinds of planets are formed.
“Thanks to its very short orbital period, and to the properties of its host star, the discovery of TOI-4860b provides a brilliant opportunity to study the atmospheric properties of a warm Jupiter and learn more about how gas giants are formed,” said SPECULOOS project scientist Mathilde Timmermans, a student at the University of Liege.
TOI-4860b was initially identified as a planet candidate by NASA’s Transiting Exoplanet Survey Satellite (TESS).
Timmermans and colleagues used TRAPPIST-South/North (TRAnsiting Planets and PlanetesImals Small Telescope), SPECULOOS (Search for Planets EClipsing ULtracOOl Stars), and MuSCAT3 (Multicolor Simultaneous Camera for studying Atmospheres of Transiting exoplanets) facilities to measure the planetary signal in several wavelengths and validated the planetary nature.
They also observed the planet just before and after it disappeared behind its host star, noticing that there was no change in light, meaning the planet was not emitting any.
The planetary nature of TOI-4860b was further confirmed through high-resolution spectroscopy obtained with the IRD spectrograph at Subaru Telescope, from which the astronomers measured a mass of 0.67 Jupiter masses.
“Under the canonical planet formation model, the less mass a star has, the less massive is the disk of material around that star,” said George Dransfield, a Ph.D. student at the University of Birmingham.
“Since planets are created from that disk, high-mass planets like Jupiter, were widely expected not to form.”
“However, we were curious about this and wanted to check planetary candidates to see if it was possible.”
“TOI-4860 is our first confirmation and also the lowest mass star hosting such a high mass planet.”
A paper describing this research was published today in the Monthly Notices of the Royal Astronomical Society: Letters.
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Amaury H.M.J. Triaud et al. 2023. An M dwarf accompanied by a close-in giant orbiter with SPECULOOS. MNRASL 525 (1): L98-L104; doi: 10.1093/mnrasl/slad097
