2023-11-29 19:50:26
An international team including scientists from the Universities of Geneva and Bern has identified a key new planetary system using the CHEOPS space telescope, according to a study published Wednesday in the scientific journal “Nature”. This discovery has particular potential for studying the composition of exoplanet atmospheres.
The system is distinguished by the fact that the six planets that compose it revolve around the star at its center in perfect harmony. The planet closest to the star completes six complete rotations in 55 days, while during exactly this same period of time, the farthest completes a single rotation. The other planets also evolve according to the same precise chain of resonance.
“We know of about 5,000 exoplanets, but systems in which resonances extend over such a long chain of six planets are extremely rare,” explained Hugh Osborn, an astrophysicist at the University of Bern and co-author of the study. Exoplanets are planets that orbit stars other than our Sun.
This feature lets us know that the system has remained largely unchanged since its formation more than a billion years ago, according to the scientist. Young planetary systems tend to move in resonance, but most lose this rhythm over time. Meteorite impacts can, for example, disrupt this fragile balance.
Great potential for science
Such systems are of particular importance for science, because their study allows conclusions to be drawn about the formation of exoplanets. “And if we know the other planets better, we will ultimately know more about the Earth” and its particularities, explains the scientist.
The star HD110067 at the center of the system has great potential for scientific research also because it is particularly bright. This makes it an ideal research candidate, because the brighter a star is, the more visible it is to telescopes, explains Hugh Osborn.
When the planets pass in front of the star at the center of the system, light filters through the planetary atmospheres, adds Jo Ann Egger, doctoral student at the University of Bern and co-author of the study, cited in a press release. Thus, astronomers can determine the chemical composition and other properties of atmospheres. For this to be possible, the star must be particularly bright, as is the case for HD110067.
The system’s planets, however, do not resemble Earth, pointed out Hugh Osborn. These mini-Neptunes are two to three times larger than Earth, have a very low density and an atmosphere rich in hydrogen, the researchers estimate.
Tess identified HD110067 in 2020
The planets orbiting HD110067 were first spotted in 2020 by a NASA satellite called Tess (Transiting Exoplanet Survey Satellite), allowing the orbits of two of them to be calculated. But it was the CHEOPS (CHAracterising ExOPlanets Satellite) space telescope that helped solve the enigma of the complete system, said Hugh Osborn.
CHEOPS had made it possible to discover another planetary system with a resonance chain in 2021, in orbit around the star TOI-178. The particular luminosity of the HD110067 system and its six planets evolving in harmony, however, make it a much more interesting object of study than TOI-178, concluded Hugh Osborn.
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