Two super-Earths have just been discovered orbiting a cool red dwarf called HD 260655 , which is only 33 light-years away. These worlds are unlikely to be habitable as we currently understand life, but the star and its exoplanets are among the closest multi-world systems to Earth.
Astronomers say the finding is excellent for studies that provide more information about what exoplanets are made of and also to assess their atmospheres, a task that will help the search for extraterrestrial life, even if the two worlds turn out to be incapable of hosting it. . “The two planets in this system are considered one of the best targets for studying the atmosphere due to the brightness of their star,” says astronomer Michelle Kunimoto of MIT’s Kavli Institute for Astrophysics and Space Research. “Is there a volatile-rich atmosphere around these planets? And are there signs of water or carbon-based species? These planets are fantastic testbeds for those explorations.”
To date, the existence of more than 5,000 exoplanets in the Milky Way has been confirmed , and astrobiologists are very interested in finding terrestrial or rocky worlds, such as Earth, Venus and Mars. In fact, one of the main criteria in the search for life elsewhere in the galaxy is to find planets similar to Earth in size and composition.
The two exoplanets orbiting HD 260655 are called HD 260655 b and HD 260655 c and were discovered because they pass between us and their star during their orbit. When exoplanets orbit the star, the star loses some light. Just these light falls were recorded by NASA’s TESS telescope for the search for exoplanets, which is designed to detect exactly these phenomena. After observing this dip in the star’s light, Kunimoto wanted to see if the star had already appeared in previous studies, and it turns out that it had. The Keck telescope spectrometer, now known as ANDES, already recorded data on it in 1998 and the CARMENES spectrometer at Calar Alto (Almería) as well.
“Each planet orbiting a star is going to have a little gravitational pull on its star,” says Kunimoto. “What we’re looking for is any slight movement of that star that might indicate a planetary-mass object is pulling on it.”
With all the data obtained by the different telescopes, the team was able to confirm that two exoplanets orbited around HD 260655 . It has also been possible to develop a complete profile of each of them.
The transit data provide information about the size, taking into account the amount of light that the star blocks. Spectral data, meanwhile, reveals the exoplanet’s mass, based on the star’s motion. Both data sets can be used to calculate the orbit of the exoplanet.
The inner exoplanet, HD 260655 b, is about 1.2 times the size and twice the mass of Earth, orbiting the star every 2.8 days. The outer world, HD 260655c, is 1.5 times the size and three times the mass of Earth, and has an orbit of 5.7 days. At those sizes and masses, their densities suggest that the two exoplanets are likely rocky worlds.
Scientists say that although the star is cooler and dimmer than the Sun, the proximity of the planets to HD 260655 means the worlds would be too hot for life as we know it. HD 260655 b has a mean temperature of 435 degrees Celsius, and HD 260655 c has a milder but still scorching 284 degrees Celsius.
Exoplanets could indeed have atmospheres and the newly deployed James Webb telescope could probe them, as one of its goals is to observe exoplanet atmospheres. Scientists point out that there may be more undiscovered exoplanets orbiting the star. “There are many multiplanetary systems that host five or six planets, especially around small stars like this one,” says astrophysicist Avi Shporer of MIT’s Kavli Institute for Astrophysics and Space Research. “Hopefully we’ll find more, and one could be in the habitable zone. That’s optimistic thinking.”
Referencia: Chu, J. 2022. Astronomers discover a multiplanet system nearby. MIT. https://news.mit.edu/2022/multiplanet-system-nearby-0615
