Bien qu'elles ne soient pas habitables du fait de leur orbite rapprochée avec leur étoile, les deux exoplanètes découvertes possèdent des dimensions et une masse similaires à celles de la Terre. © dottedyeti, Adobe Stock

Researchers report on a study accepted in the journal Astronomy and astrophysicsAnd the Discovered by space telescope tes of two outer planets Oddly enough, similar to Earth. Named HD 260655b and HD 260655c, these two super-planets orbit around a étoile woman Red, HD 260655, 33 light-years away. The distance that makes this system “The fourth closest known multiplanet system after HD 219134, LTT 1445 A and AU Mic”Study details.

Two new uninhabitable super-Earths

space telescope he-goat (Transiting Exoplanet Survey Satellite) NASA from 2018 to Detection of exoplanets Associated with the bright stars closest to us. To do this, he uses the transit method: it consists of targeting a star for a sufficient amount of time to notice differences in brightness Periodic, due to the passage of a planet in front of its host star. Using this, scientists can then track the diameter of the planet, using the steepness of the brightness and the size of its star.

In the case of the red dwarf HD 260655, it is much smaller than the red dwarf Soleil But nonetheless bright enough, the researchers also identified collective thanks to Radial velocity method. It makes it possible to deduce the effect of gravity exerted on the star, by observing the periodic changes in its luminous spectrum: when the radial velocity of the star changes, the lines ofabsorb Transformation. “Every planet in orbiting around a star that will have a small gravitational force on its starExplains Michelle Kunimoto, a postdoctoral researcher at the Massachusetts Institute of Technology (Massachusetts Institute of Technology) And who participated in the discovery of two exoplanets. “What we are looking for is very light a movement From this star which may indicate that a collective planetary body called it. »

From these data, it is possible to deduce the mass that causes this effect, and therefore the mass of the exoplanet. In combination with the diameter, the researchers infer the density of two exoplanets: since this is similar to the density of Earth, it is very likely that they correspond to rocky planetsas such MercureAnd the Venusand the earth and Mars. With a mass and volume close to Earth, this makes it a super-Earth. However, it turned out to be uninhabitable: with narrow orbits close to its star, temperatures that scientists calculated reach 435 °C for HD 260655b and 284 °C for HD 260655c. “We consider this beach to be outside the habitable zone, too warm for any water liquid is on the surfaceby M. Kunimoto

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Ideal Candidates for Atmospheric Studies

But hope is not lost for the HD 260655 system: researchers estimate that it can accommodate more than two outer planets. “There could be more planets in the system”Adds Avi Shporer, co-author of these two rocky worlds and a researcher at the Massachusetts Institute of Technology. “There are many multiplanetary systems that host five or six planets, especially around small stars like this. Hopefully we’ll find more, and we might be in the habitable zone. It’s an optimistic idea.”

They could soon be targeted by James Webb Telescopewhich will unveil its first pictures on July 12. By their proximity and the shining of their star, “Both planets in this system are among the best targets for studying the atmosphere.”, explains Mr. Kunimoto. For now, the team has decided that if they have a file ambiancethey are not extensive and consist mainly ofhydrogen. Because they are similar in density and size to Earth, the team also hopes to learn more about their formation through them.

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