Space: four questions about Trappist-1, this planetary system that could harbor life 39 light years from Earth


Excitement is at its peak within the scientific community. The James Webb telescope began observing the system of seven exoplanets discovered in 2017. This set of planets, similar to Earth and located around a star, could well fulfill the prerequisites for the possible presence of forms of life Franceinfo explains why, with Trappist-1, researchers have their heads in the stars more than ever. 1 What is Trappist-1? In 2017, an international team led by Belgian researchers from the University of Liege discovered the existence of seven exoplanets, all of which are close to Earth in size. They orbit Trappist-1, a dwarf star located 39 light-years from our solar system. Why “trappist”? In homage to the eponymous telescope located in Chile that made this observation…and also in a nod to a Belgian beer. “Trappist-1 is a red dwarf, when our Sun is a yellow dwarf,” Philippe Delorme, researcher at the Grenoble Institute of Planetology and Astrophysics (IPAG), explains to franceinfo. It is ten times less massive than our star. Red dwarfs “are the smallest and faintest stars; about 80% of stars are red dwarfs, but none are visible to the naked eye from Earth,” details Futura Sciences. 2 What are the specificities of these planets? The seven planets (named b, c, d, e, f, gih) are rocky and not gaseous, like Jupiter or Saturn. These seven planets are very close to their star. “If we were to compare with our solar system, it’s as if they were located in the orbit of Mercury,” Marc Ollivier, astronomer and director of the Institute of Space Astrophysics in Orsay (Essonne), explains to Franceinfo. This means that they orbit Trappist-1 in a very short time, between a day and a half, the closest, and 19 days, the farthest, reports Le Parisien. Another feature: this system is less than forty light years from Earth. Knowing that one light year is about 9.5 billion km, Trappist-1 is therefore almost 370 billion km from us. “It is the very close suburb of Earth, when we know that our galaxy, the Milky Way, measures 100,000 light years.” Marc Ollivier, astronomer and director of the Institut d’Astrofísica Espacial de franceinfo Finally, these planets are aligned, that is to say they lower the luminosity of the star when they make their revolution, “which makes them easier to study” , adds Philippe. Delorme 3Why does this system excite the scientific community? Since the first, in 1995, several thousand exoplanetary systems have been detected in space, but this one is causing a special excitement. “There is a conjunction between the presence of planets in the habitable zone of a star and James Webb’s ability to observe,” emphasizes Philippe Delorme. “It is the closest system physically to Earth, with planets that look like it and are aligned,” he adds. Three of the planets, e, g and g, specify Le Parisien, are therefore in the “habitable zone” of Trappist-1, that is, neither too close nor too far from it, offering temperatures suitable for the liquid. that there is water on its surface. “It doesn’t mean there’s life, but it means it’s not silly to think so.” Philippe Delorme, researcher at the Institute of Planetology and Astrophysics of Grenoble in franceinfo The system “Trappist-1 is unique, confirms to AFP Olivia Lim, PhD student at the University of Montreal. All conditions, or almost all, are favorable for the search for life outside our solar system”. However, if there is life, it could be very different from what we know on Earth, because the rotation of the planets on themselves and their revolution around Trappist-1 could be synchronous. “As for our Moon, for which we always see the same face, the star would only see one face of the planets, explains Marc Ollivier, then it would be an eternal day for this face and an eternal night for the other”. 4 Why is James Webb changing the game? The Trappist telescope in Chile, if it could find them, could not go much further. James Webb can. “It’s really the perfect tool to study the Trappist-1 planetary system, a star that emits mainly in the infrared, with the James Webb Infrared Space Telescope,” says Paris-based Michael Gillon, an astronomer at the University of Cork. Thanks to its most sophisticated instruments, it will be able to determine whether these planets have an atmosphere and, if so, its composition. How? Observing the planets as they transit around the star, that is, when they pass in front of it, from our point of view. With each passage of a planet in front of Trappist-1, James Webb will be able to observe the star’s dimming, but also break down its light, by spectroscopy, in the same way that a rainbow breaks up light Solar in various colors. . By multiplying the observations, James Webb will be able to identify, therefore, the possible presence “of traces of biomarkers, slides Philippe Delorme, either the presence of a gas or a combination of gases that we would detect in an atmosphere, which we could not explain by any other than the presence of a life form.” “The presence of methane and oxygen, like on Earth, would be really exciting”, concludes the scientist.
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