“Super Earth” which is an atmospheric laboratory was discovered

Life on the planet Earth has been made possible thanks to a combination of many factors, including a rocky composition, a suitable distance from the sun, a global magnetic field, and of course the existence of an atmosphere. Without an atmosphere there would be no liquid water on Earth, and there would be no life as we know it. The question of whether there is an atmosphere on planets in other solar systems as well, or extranets, has preoccupied researchers since the first discovery of a planet outside our solar system in 1995. Researchers are trying to answer basic questions, in which planets can have an atmosphere, and under what conditions will it continue to exist without dissipating into space.

Finding the answer to such questions is complicated and very problematic, especially when it comes to relatively small and rocky planets, i.e. similar to Earth. This is because so far very few such planets have been discovered, most of them in systems that are very difficult to explore for various reasons: some are very far away and in others their sun is very bright. An international research team has now discovered an Earth-like planet that may be the optimal laboratory for studying such atmospheres: it is only slightly larger than Earth, orbiting a red dwarf sun, and only 26 light-years away.

Gliza 486 is a red dwarf, a relatively small, cool star that is about one-third the mass and diameter of our Sun, and its brightness is almost a hundred times its own. In recent years many of the efforts to find Earth-like planets have focused on such stars, because their size makes it easier to identify even relatively small planets orbiting around them. This is how two such planets were discovered two years ago around the red dwarf Tiger Garden.

One of the significant tools in the search for exoplanets is the American space telescope TESS (acronym for Transiting Exoplanet Survey Satellite), which was launched about three years ago to scan the sky and locate planets using the eclipse method (transit) – that is, identifying stars On the passage of a planet before them. When TESS data indicates the potential for such a planet, measurements are usually made on additional instruments.

One of these devices is CARMENES (something called an acronym for Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Échelle Spectrographs). Installed in an observatory in southeastern Spain, and allows to measure with great accuracy the radial velocity (i.e., along the line of sight) of stars. When a planet orbits its sun, it attracts it slightly to it. We cannot directly see the planets because they are too small and their star light obscures them, but if viewed from a suitable angle, the star will appear to us as if it is moving away from us and approaching us intermittently. CARMENES is a spectroscope, capable of measuring the small changes in starlight following these oscillations, both in visible light and in infrared radiation, which is the main radiation emitted by red dwarfs. Thus its use increases the chance of locating signs for planets especially around red dwarfs.

The study was also joined by the team of another spectroscope, MAROON-X, a new device that has recently started operating in the North Gemini telescope in Hawaii, and is also designed to measure the radial velocity of stars.

“In fact, the CARMENES team had already begun looking at the Glyza 486 data even before we presented them with the TESS data,” Dr. Avi Sporer, an astrophysicist at the Massachusetts Institute of Technology (MIT) and a member of the TESS scientific team, explained in an interview with the Davidson Institute. “The data combination confirmed the existence of a planet slightly larger than Earth, the so-called ‘super-Earth’. Its mass is 2.8 times that of Earth and its radius is 1.3 times. He orbits his red dwarf every 35 hours. “From the weight of the mass and density data we conclude that it is a rocky planet, with a metallic core, similar to Earth and Venus, and it is assumed that it is locked with the star, meaning its self-rotation is equal to orbital time, so it constantly turns one side towards the star.”

The planet, which according to common practice is called Glyza 486b, is very close to its sun. The average distance between them is 2.6 million kilometers, less than two percent of the distance between Earth and our sun. Therefore, even though it is a relatively small and cold sun, from such a distance it is still very hot, and the temperature across the planet on the side facing the sun is about 430 degrees Celsius. Precisely this high temperature may provide an interesting snapshot regarding the planet’s atmosphere. “The question of whether this planet has an atmosphere depends on the balance between two forces,” Sporer said. “We know that strong radiation can evaporate the atmosphere and disperse it into space. On the other hand, the planet itself has gravity, in this case it is about 70 percent stronger than Earth, and the big question is whether it is strong enough to keep the atmosphere from evaporating.”

“This discovery is really ‘fox’. One hundred degrees higher, the planet’s surface was lava, and the atmosphere was made of rock vapor. If it were one hundred degrees cold, the planet would not be suitable for further research,” said Jose Caballero, an astrobiologist from Spain. And one of the leaders of the study. “A colder atmosphere emits less radiation, and is also usually thinner, so it absorbs less radiation, making it harder to study,” explains Schforer. “It’s exactly what we were looking for to test atmospheric models on rocky planets.” The first author of the research paper, Trifonov from the Max Planck Institute in Germany noted: “The proximity of this system to us is very exciting because it allows us to explore this planet in depth with the James Webb Space Telescope, which is scheduled to be launched soon, and with the next generation of Huge ground telescopes. ”

So how do you make the follow-up measurements and check if the 486b glass has an atmosphere, and if so – what is it made of? There are two methods for this, explains Forer. “In one, the wavelengths are measured exactly as the planet passes between us and the planet. A tiny portion of the star’s light is absorbed into its atmosphere, and analysis of this light composition, i.e. the absorption spectrum, allows us to identify what materials are around the planet. “For us, it is close to the edge of the star, on the way to passing behind it or emerging from the passage behind it, and this makes it possible to know the emission spectrum – what wavelengths of light are emitted from the planet, and again, decipher what materials are on and around it.”

Sounds simple? “These are very, very complex measurements, requiring very powerful and accurate spectrometers, and so far such measurements have only been made on larger planets,” Sporer noted. “However, the fact that it is a star that is a red dwarf helps us. If it were a larger sun its strong radiation would not allow us to make such measurements.”

The researchers hope to soon discover that the planet they discovered does have an atmosphere, and learn a lot from it about the processes involved in the formation of atmospheres in such systems. “This system can really be treated as a lab to learn about the planet’s atmosphere,” Sporer said. “Under what conditions is it maintained, what are its properties, how does it conduct heat around the planet, and more.”

Alongside the intriguing questions about this planet, researchers are continuing to study in depth the data of the entire system, hoping to discover more planets around Glyza 486. “So far there are no signs of more planets in this system,” Sporer noted. “But we know there are a lot of multi-planetary systems around such stars, so hopefully this is not the last planet to be discovered around this planet.”

The intriguing finding spurs researchers to continue searching for more similar planets around relatively close stars, which will open up new research fields. “Of the thousands of planets we know exist, most of them are very large and not every day discover planets of the order of Earth. Those that are close enough to us, and around a star of appropriate brightness, can be counted on two hands,” concludes Schforer. “Glisa 486b is one of the most important planets discovered using TESS, and that is exactly the mission of this space telescope: to search for planets around such stars, planets that can be explored in depth after their discovery.”

Itai Nevo, Editor-in-Chief of the Davidson Institute for Science Education website