The Exoplanet That’s Challenging Canonical Planet Formation Models

A collaborative effort from global scientists has unveiled a unique Jupiter-like planet around a dim star, TOI-4860, situated in the Corvus constellation.

This newfound gas colossus, named TOI-4860 b, stands out for a couple of reasons: Firstly, it’s unexpected to see a Jupiter-like planet around such a dim star. Secondly, it showcases a remarkable concentration of heavy elements.

The research, spearheaded by astronomers from the University of Birmingham, appears in the recent edition of the Monthly Notices of the Royal Astronomical Society.

NASA’s Transiting Exoplanet Survey Satellite first spotted potential signs of the planet as a dip in brightness when it passed its star. However, more evidence was needed to verify its planetary status.

To delve deeper, the group turned to the SPECULOOS South Observatory in Chile’s Atacama Desert. There, they gathered data across various wavelengths, confirming the planet’s existence. Additionally, observations showed no light emission from the planet when it was obscured by its star. The team then joined forces with Japanese colleagues using the Subaru Telescope in Hawai’i, which helped them ascertain the planet’s mass.

The endeavor to track this star and validate its planet was primarily driven by doctoral candidates in the SPECULOOS project.

“Under the canonical planet formation model, the less mass a star has, the less massive is the disc of material around that star,” explains George Dransfield, a doctoral candidate from the University of Birmingham.

“Since planets are created from that disc, 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.”

“I am ever thankful to the bright PhD students of our team for proposing to observe systems like TOI-4860,” remarks Amaury Triaud, an exoplanet specialist at the University of Birmingham and the study’s lead.

“Their work has really paid off since planets like TOI-4860 are vital to deepening our understanding of planet formation.

“A hint of what might have happened is hidden in the planetary properties, which appear particularly enriched in heavy elements. We have detected something similar in the host star too, so it is likely that an abundance of heavy elements catalysed the planet formation process.”

TOI-4860 b completes its rotation around its star in roughly 1.52 days. Its star’s cool nature classifies the planet as a ‘Warm Jupiter’ – a category that fascinates astronomers keen to deepen their knowledge about such planets’ origins.

Mathilde Timmermans, a member of the SPECULOOS initiative based at the University of Liege in Belgium, notes, “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.”

The team is set to use the Very Large Telescope in Chile soon, aiming to validate the existence of more such intriguing planets.”

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