Discovered a giant planet around a bright star

An international team of scientists has discovered an unusual Jupiter-sized exoplanet orbiting a low-mass star called TOI-4860located in the constellation of Corvus (The Raven).

The newly identified gas giant, named TOI-4860bis an unusual planet for two reasons: such low-mass stars are not expected to host Jupiter-like planets, and this planet appears to be particularly rich in heavy elements.

TOI-4860 b is an unusual planet in that low-mass stars are not expected to host such Jupiter-like planets, and it is rich in heavy elements.

The study, led by astronomers from the University of Birmingham, is published in the journal this week Monthly Bulletins of the Royal Astronomical Society.

The planet was originally identified using the Transiting Exoplanet Survey Satellite (TESS) as a bright spot as it passed in front of its star, but the data was insufficient to confirm the object’s nature.

The team then used the SPECULOOS Southern Observatorylocated in the Atacama Desert (Chile) to measure the object’s signal at different wavelengths and confirm its planetary nature.

SPECULOOS Southern Observatory in Chile. /ESO/G. Lambert

Astronomers also observed it just before and after it disappeared behind its host star and found that there was no change in light, meaning the planet was not emitting light.

Finally, the team worked with a Japanese group, which used the Subaru telescope in Hawaii (USA) to measure the planet’s mass for final confirmation.

Discovery of a graduate student

Tracking the star TOI-4860 and the confirmation of his planet was the initiative of a group of PhD students of the SPECULOOS project.

George Dransfieldone of these students, who has just presented his thesis, explains: “According to the canonical model of planet formation, the less massive a star is, the less massive the disk of material around it is.”

“Since planets form from this disc,” he continues, “it was expected that massive planets like Jupiter would not form. However, we were curious and wanted to check the planet candidates to see if this is possible. TOI.” -4860 is our first confirmation and also that a lower mass star hosts such a massive planet.”

For his part Amaury TriaudProfessor of exoplanetology at the University of Birmingham, who led the study, states: “Planets like TOI-4860 b are crucial for deepening our understanding of planet formation.”

Planets like TOI-4860 b are crucial to deepening our understanding of planet formation.

Amaury Triaud (University of Birmingham)

“A clue to what may have happened lies in the planetary properties, which appear to be particularly enriched in heavy elements,” he adds, “and we’ve also spotted something similar in the parent star, so it’s likely an abundance of heavier.” Elements catalyzed.” the process of planet formation”.

A day and a half to complete its orbit

The new gas giant takes about 1.52 days to complete a full orbit around its parent star, and since the parent star is cold and low-mass, the planet itself can be described as “hot Jupiter‘. This is a subclass of planets that is of particular interest to astronomers interested in learning more about the formation of these types of planets.

Mathilde Timmermansanother SPECULOOS project student working at the University of Liège (Belgium) concludes: “Thanks to its very short orbital period and the properties of its parent star, the discovery of TOI-4860 b offers an excellent opportunity to study the properties of atmospheres .” of a hot Jupiter and learn more about the formation of gas giants.


Amaury HMJ Triaud et al. “An M-Dwarf escorted by a nearby giant orbiter“. Monthly Bulletins of the Royal Astronomical Society2023

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