Two new super-worlds discovered near Earth

Researchers report in a study accepted to the journal Astronomy and Astrophysics, discovery by space telescope double exoplanets strangely similar to Earth. These two super-Earths, called HD 260655b and HD 260655c, revolve around one orbit. dwarf star red, HD 260655, 33 light-years away. A distance that makes this system “The fourth closest known multi-planet system after HD 219134, LTT 1445 A and AU Mic”details the work.

Two new, uninhabitable super-Earths

space telescope Tess (Transition Exoplanet Research Satellite) NASA since 2018 detecting exoplanets associated with the brightest stars closest to us. To do this, it uses the transit method: it consists of aiming at a star for a sufficient period of time and observing the changes in it. brightness Periodic, due to a planet passing in front of its host star. Using it, scientists can track the diameter of the planet using the intensity of the drop in brightness and the size of its star.

In the case of the red dwarf HD 260655, it’s much smaller. Sun but still bright enough, the researchers also determined mass thanks to radial velocity method. It makes it possible to understand the gravitational effect exerted on the star by observing the periodic changes in the star’s light spectrum: the star lines when the radial velocity of the star changes.Absorbation shift. “Every planet in orbit around a star there will be a small gravitational force on the star”Postdoctoral researcher Michelle Kunimoto at MIT explains (Massachusetts Institute of Technology) and those involved in the discovery of two exoplanets. “What we’re looking for is very light movement This star may indicate that a planetary mass object is firing at it. »

From these data it is possible to deduce the mass that caused this effect, hence the mass of the exoplanet. Combined with the diameter, the researchers inferred the densities of the two exoplanets: That’s similar to Earth’s, possibly corresponding to this. rocky planetsaspect Mercury, Venusworld and March. With a mass and size close to that of Earth, this makes them super-Earths. However, they turned out to be uninhabitable: with narrow orbits close to their star, temperatures calculated by scientists reach 435 °C for HD 260655b and 284 °C for HD 260655c. “We see this beach outside of the habitable zone as too hot for any water. liquid exists on the surface”Mr. Kunimoto explains.

Ideal candidates for an atmospheric study

But hope is not lost for the HD 260655 system: the researchers estimate that the system could accommodate more than two. exoplanets. “There may be more planets in the system”adds Avi Shporer, a co-explorer of these two rocky worlds and a researcher at MIT. “There are many multi-planet systems that host five or six planets, especially around small stars like this one. I hope we find more and be in the habitable zone. It is an optimistic thought. »

They may soon be targeted by them. James Webb telescopewho will reveal their first images on July 12. With their proximity and the brilliance of their stars, “Each of the two planets in this system counts among the top targets for atmospheric study”, Mr. Kunimoto explains. For now, the team, if a atmosphereis not exhaustive and mainly consists of:hydrogen. Similar to Earth in density and size, the team hopes to learn more about its formation through them.

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