🔭 These planets change orbit under the eyes of astronomers

The planetary system TOI-201, located 370 light-years from Earth, exhibits a rare phenomenon: the orbits of its three planets are evolving so quickly that astronomers can observe them in real time. This unprecedented behavior challenges current models of planetary formation.

The star TOI-201 is 1.3 times more massive than the Sun and has an equivalent diameter. Orbiting around it are three distinct planets: a rocky super-Earth, six times more massive than Earth, with a year lasting 5.8 days; a gas giant half the mass of Jupiter, named TOI-201b, which completes its orbit in 53 days; and another giant, sixteen times more massive than Jupiter, with a year of nearly 2,883 days.


These worlds were detected thanks to NASA's TESS satellite and the ASTEP observatory in Antarctica. Installed on the Antarctic plateau, ASTEP takes advantage of the polar nights to observe continuously. By combining the data, researchers detected the planetary transits. TESS also spotted the rare transit of the outer planet.

These observations made it possible to measure shifts in the transits of the inner planet TOI-201b. A shift of about thirty minutes was observed, a sign of intense dynamic interactions.

The uniqueness of this system lies in the highly inclined and elliptical orbit of the farthest planet. Its gravity disturbs the orbits of the inner planets, altering the predicted timing of their transits. In about 200 years, the planets will no longer align in front of their star for observation from Earth. Amaury Triaud notes that most planetary systems are homogeneous, while TOI-201 exhibits great diversity. Tristan Guillot adds that this indicates an ongoing orbital reorganization.

These observations provide a glimpse into the dynamic processes that follow planet formation. In our Solar System, orbits are nearly coplanar, but here each planet is different, indicating an ongoing reorganization. Researchers hope that studying TOI-201 will help better understand how planetary systems evolve over long periods. In particular, the observed gravitational interactions could explain the diversity of exoplanets already discovered.

The study of the TOI-201 system is just beginning. Scientists plan to observe future transits to better understand the dynamics at play. This work could also help explain why some planetary systems are so different from one another, like our own. The team hopes that long-term monitoring will reveal patterns in orbital changes. These discoveries could refine models of planet formation and migration.