Researchers discover planetary system evolving in real time - thanks to one-of-a-kind telescope located in the Antarctic Plateau.
Artistic illustration of ASTEP facility
Astronomers have found a system of planets in a rare and puzzling configuration - three very different orbiting objects which interact gravitationally and whose orbits are changing fast enough to be seen in real time.
Scientists from the University of Birmingham, Observatoire de la Côte d’Azur, and the European Space Agency (ESA) used the ASTEP (Antarctic Search for Transiting ExoPlanets) facility - working with NASA’s TESS space telescope and the LCOGT network of telescopes in Chile, Australia, and South Africa - to discover the new planetary system which has been called TOI-201.
Publishing their findings in Science, researchers uncover a rare planetary system whose orbits are changing fast enough to be seen in real time. TOI-201 behaves in a way astronomers have never seen before.
Most planetary systems appear as ‘peas in a pod,’ meaning the planets have a similar range of parameters and share a similar orbital plane. This is not the case in the TOI-201 system, which contains three orbiting objects very distinct from one another, and which interact gravitationally.
The international research team, led by scientists from the University of New Mexico, discovered three very different worlds orbiting a star 30% more massive (how much mass the star has) and 30% bigger than the sun, and about a tenth of the sun’s age. The system comprises of:
Professor Amaury Triaud, from the University of Birmingham, said: “Most planetary systems appear as ‘peas in a pod,’ meaning the planets have a similar range of parameters and share a similar orbital plane. This is not the case in the TOI-201 system, which contains three orbiting objects very distinct from one another, and which interact gravitationally.”
Most planetary systems are relatively stable on timescales of millions or billions of years. TOI-201 is different, with the massive outer object’s highly stretched and tilted orbit, and its gravity pulling strongly on the inner planets. This causes:
Tristan Guillot, an astronomer at the Observatoire de la Côte d’Azur, and the ASTEP lead said: “In the solar system, almost all planets are coplanar, but here, this is not the case and each planet is different. This points to some active orbital reorganisation within the system, providing us a glimpse of what happens shortly after planet formation.”
Members of the ASTEP research team with the telescope in Antarctica.
ASTEP uses the very long polar nights in Antarctica during the winter, and the extremely favourable weather found at Concordia station, which is 1,200km inland and installed on top of a 3.2km deep glacier. Concordia station is one of Earth’s most isolated places and temperatures in winter can reach down to -80ºC.
Lead author Ismael Mireles, a PhD candidate at the University of New Mexico said: “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. This helps scientists understand how planetary systems like our own Solar System form and evolve over time.”
NASA’s TESS space telescope captured an extraordinarily rare transit for the outer object, while telescopes in Chile and Australia also noticed the star had been pulled suddenly by the gravity of the outer object as it zoomed through its closest and fastest approach. Consistent signals were also obtained from ESA’s Gaia satellite.
Professor Triaud said: “Usually, planets are like metronomes with each transit in front of the star happening exactly one orbital period after another. However, we were following TOI-201b, and suddenly the planet started transiting about half an hour late. This sudden jump was very surprising, and we reported our observations. Other astronomers around the globe noticed intriguing signals too, and by working together, the team could start to understand this system.
“This discovery was enabled by having a telescope in Antarctica. Whilst the logistics involved are difficult, its unique situation and its access to optimal astronomical conditions are key to studying exoplanetary systems with long orbital periods such as TOI-201.”
Thanks to its elongated orbit, TOI-201b might eventually be directly observed, where astronomers would collect light from the remnant heat of the planet’s formation. Should this be the case, TOI-201b will become a rare ‘Rosetta-stone planet’, able to be investigated using most detection and characterisation methods and enabling comparisons and benchmarking between them.
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‘Uncovering the Rapidly Evolving Orbits of the Dynamic TOI-201 System’ – Mireles et al is published in Science.
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Professor of Exoplanetology
Staff profile for Professor Amaury Triaud
