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[EN VIDÉO] Tess launched to conquer new habitable lands Exoplanet hunter Tess was launched by a SpaceX Falcon 9 rocket on April 18, 2018. This successor to Kepler will settle far from Earth to monitor 200,000 stars for two years By regularly measuring the luminosity of each, this observatory will detect the possible passages of the planets (transits). Astronomers will then expand the list of habitable exoplanet candidates, which will be studied by the next generation of telescopes. Two new super-Earths are added to the list of discovered exoplanets today. Unearthed by the telescopes of the Speculoos project (Search for habitable Planets EClipsing ULtra-cOOl Stars) which consists of searching for habitable planets around faint and cold stars, they orbit the star LP 890-9, also called TOI-4306 or Speculoos -2. This small red dwarf star is about 100 light-years from Earth, and it happens to be the second coldest star around which exoplanets have been found! After Trappist-1, the coolest star known to host planets, 7 to its credit! The two new discoveries were detailed in a study published in the journal Astronomy & Astrophysics. Orbital periods of 2 and 8 days, but one of the two is in the habitable zone. The two planets orbit rapidly around their star: the the inner one completes a complete revolution in only 2.73 days, and the other in 8.46 days! The inner planet, called LP 890-9b, is 30% larger than Earth. Initially detected by NASA’s Tess (for Transiting Exoplanet Survey Satellite) space telescope, which detects nearby exoplanets using the transit method, it was confirmed and then characterized using Speculoos transits, simultaneously monitoring the brightness of thousands of stars, looking for faint obscurations that could be caused by planets passing in front of their stars”, explains Laetitia Delrez in a press release, first author of the study and postdoctoral researcher at the “University of Liège”. However, it is often necessary follow up with ground-based telescopes. to confirm the planetary nature of the detected candidates and to refine measurements of their sizes and orbital properties. Indeed, the Tess telescope is poorly sensitive to the infrared, and the star LP 890-9 emits mainly in this area. As for the second, outermost planet, it is this one that attracts the most attention from researchers: the bat jet LP 890-9c and similar in size to LP 890-9b, would be located in the habitable zone even though it has a very short orbital period – only 8.5 days! very close to its star, at a distance about 10 times shorter than that of Mercury around our Sun, the amount of stellar radiation it receives is still small, and could allow the presence of liquid water in the surface of the planet, as long as it has a sufficient atmosphere, explains Francisco J. Pozuelos, co-author of the study. and researcher at the Institute of Astrophysics of Andalusia. This is because the star LP 890-9 is about 6.5 times smaller than the Sun and has a surface temperature half that of our star. This explains why LP 890-9c, despite being much closer to its star than Earth from the Sun, could still have life-supporting conditions. »A prime target for James-Webb’s search for life This discovery is therefore encouraging for the search for life: the star LP 890-9 becomes one of James-Webb’s prime targets, after the planets of the Trappist-1 system. ! According to Laetitia Delrez, it would even be a target of choice, in particular because of the greater chemical traceability of its atmosphere, and therefore it could have an atmosphere particularly rich in water vapor, which would strengthen its atmospheric signals. Furthermore, models often differ as to the exact position of this inner habitable zone boundary depending on the characteristics of the star. Therefore, the discovery of LP 890-9c offers a unique opportunity to better understand and constrain the habitable conditions around the smallest and coldest stars in our solar neighborhood,” he concludes. Interested in what you just read?
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