An unexpected Jupiter-sized planet has been found around the low-mass star TOI-4860 in the Corvus constellation by a global team of astronomers.
Because stars with such low masses are not predicted to have planets the size of Jupiter, and because the recently discovered gas giant, TOI-4860 b, appears to be exceptionally enriched in heavy elements, the planet is peculiar.
Today, the study—led by astronomers from the University of Birmingham—was released in a letter that appeared in the Monthly Notices of the Royal Astronomical Society.
The planet was first discovered by NASA’s Transiting Exoplanet Survey Satellite as a reduction in brightness while transiting in front of its host star, but that information was not enough to determine for sure that it was a planet.
The team confirmed the planetary nature by measuring the planetary signal at various wavelengths using the SPECULOOS South Observatory, which is situated in Chile’s Atacama Desert. The planet was also spotted shortly before and after it vanished below its host star, and the scientists saw that there was no difference in light, indicating that the planet was not emitting any. Finally, the team used the Subaru Telescope in Hawaii to work with a Japanese team. To completely confirm the planet’s mass, they measured it collectively.
A team of Ph.D. students working on the SPECULOOS project decided to follow this star and confirm its planet.
One of those Ph.D. candidates, George Dransfield, says that according to the conventional concept of planet formation, the mass of a star determines how massive the disc of material surrounding it is.
“High-mass planets like Jupiter were largely anticipated not to exist since planets are formed from that disc. However, we were interested in this and sought to investigate planetary prospects to determine whether it was feasible. Our first confirmation comes from TOI-4860, which is also the lowest mass star to support a planet with such a high mass.
“I am ever grateful to the bright Ph.D. students of our team for proposing to observe systems like TOI-4860,” said Amaury Triaud, professor of exoplanetology at the University of Birmingham and study’s principal investigator. Their efforts have paid off handsomely since planets like TOI-4860 are crucial to understanding planet creation.
“The planetary qualities, which seem unusually wealthy in heavy metals, hide a hint of what might have transpired. Since we also found evidence of something similar in the host star, it is most likely that an abundance of heavy elements accelerated the process of planet formation.
The new gas giant’s orbit around its host star takes around 1.52 days to complete, however because the star is a frigid low mass star, the planet itself can be referred to as a “warm Jupiter.” Astronomers who want to expand on their preliminary findings and discover more about how these kinds of planets are generated are particularly interested in this subclass of planets.
The conclusion of Mathilde Timmermans, a different SPECULOOS project participant who studies at the University of Liege in Belgium, is that “the discovery of TOI-4860 b provides a brilliant opportunity to study the atmospheric properties of a warm Jupiter and learn more about how gas giants are formed thanks to its very short orbital period, and to the properties of its host star.”
The team recently received telescope time at the Very Large Telescope in Chile, which they expect to utilize to confirm a number of additional planets with comparable characteristics.
More information: Amaury Triaud et al, An M-dwarf accompanied by a close-in giant orbiter, Monthly Notices of the Royal Astronomical Society (2023). An M dwarf accompanied by a close-in giant orbiter with SPECULOOS.