TOI-2096, a newly discovered planetary system by astronomers from the University of Liege!

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 A study led by researchers from the University of Liège, using observations from NASA's TESS telescope, has discovered a system consisting of two planets slightly larger than Earth that orbit a cold star in synchronous fashion. The system has been named TOI-2096 and is located 150 light years from Earth. The discovery has been published in the journal Astronomy & Astrophysics.

 This discovery is the result of close collaboration between European and American universities and was facilitated by the TESS (Transiting Exoplanet Survey Satellite) mission, which aims to search for planets on bright star orbits near us. "TESS monitors the entire sky for transits, meaning it measures the brightness of hundreds of thousands of stars to look for very small drops in brightness that might be caused by a planet passing in front of its star in the detector's line of sight. However, despite the efficiency of the TESS mission in detecting new worlds, it requires support from telescopes on Earth to confirm the planetary nature of the signals detected," explained Pozuelos, the first author of the paper and an astrophysicist who was formerly a member of the University of Liège's ExoTIC laboratory (Astrobiology Research Unit/Department of Science).

 The TOI-2096 planetary system consists of two planets, TOI-2096 b and TOI-2096 c. These two planets were observed by multiple telescope arrays, allowing them to be confirmed and characterized. Most of the transits were obtained by telescopes from the TRAPPIST and SPECULOOS projects led by the University of Liège. Mathilde Timmermans, a doctoral student at the University of Liège's ExoTIC laboratory and the second author of the paper, stated, "Through detailed analysis of the data, we discovered that these two planets are in orbital resonance: on each orbit of the outer planet, the inner planet completes two orbits around the star. Therefore, their periods are very close multiples of each other, with the period of planet b being about 3.12 days and that of planet c being about 6.38 days. This configuration is very special and leads to strong gravitational interactions between the planets. These interactions have a delayed or accelerated effect on the planets passing in front of their star and may lead to the measurement of the planets' masses using more powerful telescopes in the near future."

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 Scientists behind this discovery estimate that the radius of planet b (closest to its star) is 1.2 times that of Earth, hence it is called a "super-Earth". Its characteristics may be similar to Earth: a rocky planet, possibly surrounded by a thin atmosphere. Similarly, planet c has a radius 1.9 times that of Earth and is 55% that of Neptune, which may make it a "mini-Neptune", a planet with a core of rock and ice surrounded by an extended atmosphere rich in hydrogen or water, like Uranus and Neptune in our solar system. These sizes are very interesting because the number of planets between 1.5 and 2.5 times the radius of Earth is less than theoretically predicted, making these planets very rare. Mathilde Timmermans pointed out, "Given the size of these planets, they are of crucial importance. The formation of super-Earths and mini-Neptunes is still a mystery today. Several formation models try to explain it, but none really matches what we observe. TOI-2096 is the only system discovered so far with a super-Earth and a mini-Neptune, and the sizes of these two systems are exactly contradictory to the models. In other words, TOI-2096 may be the system we have been looking for, which can help us understand how these planetary systems form."

 "More importantly, these planets are among the most suitable planets of their kind for studying their possible atmospheres," explained Pozuelos. "Due to the relative size of these planets to their host star and the brightness of the star, we find that this system is one of the best candidates for studying its atmosphere using the JWST space telescope. We hope to quickly complete this work through coordination with other universities and research centers. These studies will enable us to confirm whether there are atmospheres around planets b and c, giving us an indication of their formation mechanism."

 From nebulae to the TRAPPIST-1 planets, to "super-Earths," protoplanets, and the TOI-2096 planetary system, astronomers at the University of Liège have been exploring forward, constantly revealing the mysteries of the universe with new discoveries. This is also one of the reasons why University of Liège students are proud and looking forward to more surprises from astronomers in the future.