The TOI-201 system features a super-Earth, a warmer Jupiter, and a massive brown dwarf, showcasing unique orbital periods of 5.8, 53, and 2,900 days, respectively.
Artistic representation of the warm giant exoplanet TOI-201b and its parent star. Image credit: Sci.News.
TOI-201 is a brilliant F-type star located 372 light-years away in the constellation Pictor.
With a size and mass 32% greater than that of the Sun, TOI-201 is approximately 870 million years old.
Also referred to as HD 39474 and TIC 350618622, this star hosts at least three planetary companions: TOI-201b, c, and d.
Dr. Ismael Mireles, a candidate at the University of New Mexico, stated, “The goal was to characterize the TOI-201 planetary system to understand not only what planets exist, but also how they interact dynamically.”
This research aids scientists in understanding the formation and evolution of planetary systems akin to our own solar system.
TOI-201d is a rocky super-Earth, approximately 1.4 times Earth’s size and about six times its mass, completing an orbit every 5.8 days.
TOI-201b is a warm Jupiter-like exoplanet, with half the mass of Jupiter, orbiting every 53 days.
Lastly, TOI-201c is a brown dwarf, the system’s most massive entity excluding the star, with a highly elliptical, broad orbit of around 8 years, significantly influencing the system’s dynamic characteristics. It is also the longest-period transiting object discovered to date.
Dr. Mireles noted, “TOI-201c is unique due to its extensive orbital period of about 7.9 years and its positioning within a system that includes two inner planets.”
“Most known transiting brown dwarfs are in much closer proximity to their stars.”
Diana Dragomir, a professor at the University of New Mexico, remarked, “TOI-201c’s mass is at the threshold between giant planets and brown dwarfs, raising questions regarding whether this object formed as a planet or a star.”
“This system offers one of the few opportunities to observe planetary orbits undergoing changes on human timescales,” Mireles added.
“This presents a rare chance to learn about the dynamic life of a planetary system in real-time. In 200 years, only two out of the three objects will still be transiting.”
The significance of the TOI-201 system lies in the fact that astronomers can monitor its changes in real time.
Professor Dragomir explained, “This was unexpected because if planets formed in the protoplanetary disk aligned with their star’s early life, their orbits would typically align, like those in our solar system.”
The next key question for TOI-201 is about the origins of these tilted orbits among the three objects.
After 200 years, TOI-201d will cease transiting, followed by TOI-201b, and eventually TOI-201c will stop as well.
However, they oscillate between transiting and non-transiting states, suggesting they will resume transiting in several thousand years.
Predictions indicate TOI-201c’s next transit will occur on March 26, 2031, offering a rare chance for global follow-up observations, including opportunities for citizen scientists.
“A large, multi-year team effort was essential to study this complex system,” Mireles concluded.
A publication detailing the survey results appeared in the journal Scientific Progress.
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Ismael Mireles et al., 2026. Unveiling the dynamic evolution of the TOI-201 system. Scientific Progress 12(16); doi: 10.1126/sciadv.aef2618
Source: www.sci.news
