An international team with Bernese participation has identified two “super-Earth” type planets around an “ultra-cold” star. One of them could harbor water in liquid form.

A first planet, called LP 890-9b (or TOI-4306b), the innermost of the system, was initially identified by the space mission TESS (Transiting Exoplanet Survey Satellite) of NASA, dedicated to the search for exoplanets orbiting nearby stars.

This planet, which is about 30% larger than Earth, completes an orbit around The research team, led by Laetitia Delrez, an astrophysicist at the Belgian University of Liège, used the consortium’s ground-based telescopes Speculoos (Search for habitable Planets EClipsing ULtra-cOOl Stars) to confirm and characterize this planet. She also probed the system for other planets that might have been missed by TESS. This quest detected a second, previously unknown star in 2.7 days.

A unique opportunity”

This second planet, LP 890-9c, is similar in size to the first – about 40% larger than Earth – but has a longer orbital period of about 8.5 days. However, this orbital period places the planet in the so-called “habitable” zone around its star.

“Although this planet is very close to its star, at a distance about ten times less than that of Mercury around our Sun, the amount of stellar radiation it receives remains small, and could allow the presence of liquid water at the surface, as long as it has a sufficient atmosphere”, explains Francisco J. Pozuelos, researcher at the Institute of Astrophysics of Andalusia and one of the people who co-wrote the article.

“This planet receives roughly the same amount of solar radiation as our Earth,” said Robert Wells of the University of Bern, quoted in a press release from the latter on Wednesday. More detailed observations, for example with the James Webb Space Telescope, will be needed to find out more, adds the scientist.

“The discovery of LP 890-9c offers a unique opportunity to better understand the conditions of habitability around the smallest and coldest stars in our solar neighborhood”, concludes Laetitia Delrez. The system is about a hundred light years from Earth. These jobs are published in the journal Astronomy & Astrophysics.

Discovery of 2 planets slightly larger than Earth, one of which could be habitable!

The 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 one, this observatory will detect the possible passages of planets (transits). Astronomers will then extend the list of candidates for habitable exoplanets, which will be studied by the next generation of telescopes.

Of them new super-earths are added today to the table of exoplanets discoveries. Discovered thanks to telescopes of the Speculoos (Search for habitable Planets EClipsing ULtra-cOOl Stars) project, which consists of looking for habitable planets around dim and cold stars, they orbit around thestar LP 890-9, also called TOI-4306 or Speculoos-2.

This little dwarf star red is about 100 light years Earth, and happens to be the second coldest star around which we have never found exoplanets! After Trappist-1, the coldest star known to host planets, 7 to its credit! The two new findings were detailed in a study published in the journal Astronomy & Astrophysics.

Orbital periods of 2 and 8 days, yet one of the two is in the zone of habitability

The two planets orbit their star rapidly: the innermost completes a full rotation in just 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 the space telescope Tess (for Transiting Exoplanet Survey Satellite) from NASA, which detects nearby exoplanets using the method of transitsit was then confirmed, then characterized, thanks to Speculoos.

TESS search for exoplanets using the transit method, simultaneously monitoring the brightness of thousands of stars, looking for the slight obscurations that could be caused by planets passing in front of their stars”, explains Laetitia Delrez in a communicatedfirst author of the study and postdoctoral researcher at the University of Liège.

“However, follow-up with ground-based telescopes is often needed to confirm the planetary nature of detected candidates and refine measurements of their orbital sizes and properties. Indeed, the Tess telescope is not very sensitive to infraredand the star LP 890-9 emits mainly in this area.

As for the second planet, the outermost, it is this which attracts the most attention from researchers: baptized LP 890-9c and of a size similar to LP 890-9b, it would be located in the habitable zone although it has a very short orbital period: only 8.5 days! “Although this planet orbit very close to its star, at a distance about 10 times shorter than that of Mercury around our Sunthe amount ofirradiation stellar that it receives is still weak, and could allow the presence of water liquid on the surface of the planet, provided you have a atmosphere sufficient, 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 is to the Sun, might still have conditions that support life. »

A prime target for the search for life by James-Webb

This discovery is thus encouraging for the search for life: the star LP 890-9 becomes one of the main targets of choice for James Webb, after the planets of the Trappist-1 system! According to Laetitia Delrez, she would even be a prime target, especially for the biggest traceability chemistry of its atmosphere.

“This comparison, however, ignores the fact that LP 890-9c is located near the inner limit of the habitable zone and therefore could have a particularly water vapor-rich atmosphere, which would then enhance its atmospheric signals. In addition, models often differ as to the exact position of this interior limit of the habitable zone depending on the characteristics of thestar. The discovery of LP 890-9c therefore offers a unique opportunity to better understand and constrain the conditions of habitability around the smallest and coldest stars in our solar neighborhood,” she concludes.

SCIENCE

Discovery of a potentially habitable “super-Earth” planet

An international team of scientists, led by Laetitia Delrez, astrophysicist at the University of Liège (ULiège), has just announced the identification of two “super-Earth” type planets. One of them turns out to be potentially habitable, relays the Liège university on Wednesday morning by means of a press release.

A first planet, answering to the sweet name of LP 890-9b (or TOI-4306b)the innermost of the system had been initially identified by the space mission Tess (Transiting Exoplanet Survey Satellite) of NASA, dedicated to the search for exoplanets in orbit around nearby stars. This planet, which is approximately 30% larger than Earth, completes an orbit around its star in just 2.7 days.

A discovery by ULiège researchers

The ULiège researchers used their terrestrial telescopes Speculoos (Search for habitable Planets EClipsing ULtra-cOOl Stars) to confirm and characterize this planet, and also probe the deep system for other planets that may have been “missed” by Tess. “The observations of LP 890-9 obtained by Speculoos proved to be fruitful since they not only helped to confirm the first planet, but have also made it possible to detect a second, previously unknown,” rejoices the university.

This second planet, LP 890-9c (renamed Speculoos-2c by ULiège researchers), has a size similar to the first (about 40% larger than the Earth) but presents a longer orbital period of about 8.5 days. However, this orbital period places the planet in the so-called “habitable” zone around its star.

Potentially habitable

“Although this planet is very close to its star, at a distance about 10 times less than that of Mercury around our Sun, the amount of stellar radiation it receives remains low, and could allow the presence of liquid water on the surface of the planet, as long as it has a sufficient atmosphere“, explains Francisco J. Pozuelos, researcher at the Institute of Astrophysics of Andalusia and one of the main co-authors of the article.

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