Astronomers have discovered 2 super-Earths orbiting a nearby star

Two new worlds of likely rocky mineral goodness have just been found orbiting a star near our own cosmic environment.

The two newly discovered exoplanets are so-called super-Earths — larger than Earth but smaller than an ice giant — orbiting cool red dwarf star HD 260655, just 33 light-years away.

While the worlds are unlikely to be habitable, given our current understanding of life, the star and its exoplanets are among the closest multi-world systems to Earth.

This makes it an excellent target for follow-up studies to try to understand what the exoplanets are made of and to assess their atmospheres – an effort that will aid our search for extraterrestrial life, even if the two worlds prove unable to cope with it. self-host.

“Both planets in this system are each considered some of the best targets for atmospheric study because of the brightness of their star,” says astronomer Michelle Kunimoto from MIT’s Kavli Institute for Astrophysics and Space Research.

“Is there a volatile-rich atmosphere around these planets? And are there any signs of water- or carbon-based species? These planets are fantastic testbeds for those explorations.”

To date, more than 5,000 exoplanets have been confirmed in the Milky Way, and astrobiologists are very interested in finding terrestrial or rocky worlds such as Earth, Venusand Mars

We have a sample size of exactly one world known to harbor life — our own — so finding planets similar in size and composition to Earth is one of the most important criteria when looking for life elsewhere in the galaxy. .

However, rocky exoplanets are relatively small in size and mass, making them more difficult to detect; most exoplanets we have been able to measure so far often fall into the category of giants† Rocky worlds – and better yet, nearby rocky worlds – are highly sought after.

The two worlds orbiting HD 260655—named HD 260655 b and HD 260655 c—were discovered because they pass between us and their star during their orbit. The faint dips in starlight resulting from these exoplanetary transits were captured by NASA’s exoplanet hunting telescope TESS, which is designed to detect just such phenomena.

When Kunimoto saw these transit dips in the TESS data, the next step was to see if the star had appeared in previous studies — and it did.

The High Resolution Echelle Spectrometer on the Keck telescope (now known as ANDES) had publicly available data going back to 1998. Another spectrometer, CARMENES at the Calar Alto Observatory in Spain, the star had also been recorded.

This makes a huge difference to the science of exoplanets: spectrographic data can reveal whether a star is moving on the spot or not.

“Any planet orbiting a star will exert a little gravitational pull on its star,” Kunimoto says:† “What we’re looking for is any little movement of that star that could indicate that an object of planetary mass is pulling on it.”

Between the TESS data and the data from HIRES and CARMENES, the team was able to confirm that two exoplanets orbiting HD 260655. In addition, both data sets allowed the team to build a comprehensive profile of the two exoplanets.

Transit data provides a physical size based on how much light is blocked from the star; and spectral data shows how massive the exoplanet is, based on how much the star moves. Both datasets can be used to calculate the orbit of the exoplanet.

The innermost exoplanet, HD 260655 b, is about 1.2 times the size of Earth and twice as massive as Earth, and orbits the star every 2.8 days. The outer world, HD 260655 c, is 1.5 times the size and three times the mass of Earth, and has an orbit of 5.7 days.

With those sizes and masses, their densities suggest the two exoplanets are likely rocky worlds.

Unfortunately, although the star is cooler and fainter than the sun, the planets’ proximity to HD 260655 means the worlds would be far too hot for life as we know it. HD 260655 b has an average temperature of 435 degrees Celsius (816 Fahrenheit) and HD 260655 c is a milder but still scorching 284 degrees Celsius (543 degrees Fahrenheit).

“We consider that range outside the habitable zone, too warm for liquid water to exist at the surface,” Kunimoto says:

However, both exoplanets may still have atmospheres, which should be ripe for investigation by the newly deployed James Webb Space Telescope, which, among other things, peers at the atmospheres of exoplanets as one of its mission targets.

In addition, there could even be additional exoplanets orbiting the star that we have not yet discovered.

“There are many multiplanet systems with five or six planets, especially around small stars like this one,” says astrophysicist Avi Shporer from MIT’s Kavli Institute for Astrophysics and Space Research.

“Hopefully we’ll find more, and maybe there’s one in the habitable zone. That’s optimistic thinking.”

The team presented its findings at the 240th Meeting of the American Astronomical Society

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