The research was led by Ismael Mireles, a PhD candidate in the UNM Department of Physics and Astronomy advised by Professor Diana Dragomir.
"The goal was to characterize the TOI-201 planetary system to understand not just what planets are there, but how they interact with each other dynamically," said Mireles. "This helps scientists understand how planetary systems like our own Solar System form and evolve over time."
The super-Earth, TOI-201 d, is a rocky planet roughly 1.4 times Earth's size and approximately six times Earth's mass, completing one orbit every 5.85 days. It sits very close to its host star and is likely too hot to support liquid water.
TOI-201 b is a warm Jupiter - a gas giant about half the mass of Jupiter orbiting every 53 days. Warm Jupiters occupy a middle ground between close-in hot Jupiters with orbits of just a few days and distant cold gas giants like Jupiter with orbital periods of roughly 12 years. They are scientifically interesting because astronomers do not fully understand how they arrived at their current orbital positions.
The most massive body in the system besides the star is the brown dwarf TOI-201 c, which sits on a wide, highly elliptical orbit of approximately 7.9 years - making it the longest-period transiting object ever discovered. A brown dwarf occupies the boundary between a massive planet and a true star, exceeding 13 Jupiter masses but too small to sustain hydrogen fusion in its core.
"TOI-201 c is unique because of its extremely long orbital period and its location in a system with two interior planets," Mireles said. "Most known transiting brown dwarfs orbit much closer to their stars."
The gravitational influence of TOI-201 c is responsible for most of the system's dynamic behavior. The planets' orbits are tilted relative to each other and are slowly pulling one another into new orientations - a process observable on human timescales rather than the millions of years typical of most planetary systems.
"This is one of only a handful of systems where planetary orbits can be watched actively changing on human timescales. It offers a rare real-time window into the dynamic lives of planetary systems," Mireles said.
The misaligned orbits pose their own puzzle. Planets forming in the plane of a protoplanetary disk are expected to have aligned orbits, as seen in the Solar System. How TOI-201's three bodies ended up with such tilted configurations remains an open question.
To confirm the system's architecture, the researchers combined four observational techniques: radial velocity spectroscopy using the CORALIE, HARPS, PFS, and FEROS spectrographs in Chile and the MINERVA-Australis facility in Australia; transit photometry from NASA's TESS space telescope, the ASTEP telescope in Antarctica, and the LCOGT global telescope network; transit timing variations to detect gravitational perturbations between bodies; and astrometry using data from the Hipparcos and Gaia space missions.
The ASTEP telescope's location in Antarctica proved particularly valuable. "Whilst the logistics involved are difficult, the telescope's unique location and access to optimal astronomical conditions are key to studying exoplanetary systems with long orbital periods such as TOI-201," said Professor Triaud of the University of Birmingham.
The orbital evolution of the system has a defined endpoint. Within 200 years, TOI-201 d will stop transiting. A few hundred years after that, the warm Jupiter will follow. The brown dwarf will eventually cease transiting as well, though all three bodies will resume transiting thousands of years in the future as the system cycles through its configurations.
The next transit of TOI-201 c is predicted for March 26, 2031, providing a rare opportunity for follow-up observations worldwide, including by citizen scientists.
"Every new transit observation and every new radial velocity measurement gradually lifted the veil and helped uncover the three-dimensional architecture of the TOI-201 system. And this unique architecture is at the heart of the system's previously unseen dynamical interactions," Mireles concluded.
Research Report:Uncovering the rapidly evolving orbits of the dynamic TOI-201 system
Related Links
University of New Mexico
Lands Beyond Beyond - extra solar planets - news and science
Life Beyond Earth
| Subscribe Free To Our Daily Newsletters |
| Subscribe Free To Our Daily Newsletters |
