Scientists have finally discovered a rocky exoplanet, from which, it is possible to study the composition of the atmosphere using spectral methods. And it is located at a distance of only 26 light-years from us.
Since the first exoplanet was discovered in the 1990s, astronomers have identified thousands of planets outside the solar system, and have always dreamed of finding one from which they could “see” the atmosphere and study its composition.
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To detect the atmosphere around exoplanets, scientists look for subtle changes in the star’s wavelength spectrum as the planet passes in front of it. Certain wavelengths are absorbed or emitted by elements of the atmosphere, which appear as darker or brighter lines in the spectrum and can be used to determine the chemical composition of the atmosphere.
If the exoplanet is located far from us, then these signals will be very weak. The signal strength also depends on the brightness of the star itself – the brighter it is, the stronger the spectrum. And another important factor is the frequency of the exoplanet’s revolution around the parent star: if the orbit is short, you can observe many transits in a short time, and then add them up to amplify the signal.
Participants in the CARMENES international project to search for low-mass planets near red dwarfs, in which eleven research institutes from six countries participate, reported that they have found an ideal candidate for such a study – the planet Gliese 486b in the constellation Virgo.
For their analysis, the authors used data from NASA’s Transiting Exoplanet Survey Satellite (TESS) and telescopes in Spain, the United States, Chile, and Hawaii.
Gliese 486 b belongs to the super-earth class, it is a rocky planet that is larger in size than Earth, but smaller than ice giants such as Neptune and Uranus. It orbits a red dwarf star, one of our closest galactic neighbors, 26 light-years away.
“This is the kind of planet we’ve been dreaming about for decades,” quoted in a press release from the University of New South Wales, the words of one of the study’s authors, Dr. Ben Montet.
Red dwarfs are the most common stellar type, making up about 70 percent of all stars in the universe. They are much more likely to have rocky planets than stars like the Sun.
“Based on these numbers, red dwarfs may have a better chance of finding life in the universe, but there is a catch,” says Dr. Montet.
“Red dwarfs are known to have a lot of stellar activity, like flares and coronal mass ejections. This kind of activity threatens to destroy a planet’s atmosphere”
Scientists estimate that the mass of Gliese 486b is about 30 percent larger than Earth, and its temperature is about 430 degrees Celsius. Perhaps, the authors of the study suggest, streams of incandescent lava flow over the surface of the planet, and it is unlikely that life can exist there in the form in which we are used to understanding it. But if an atmosphere is found near Gliese 486b, it will give an idea of the early stages of the evolution of rocky planets in general and the Earth in particular, the researchers say.
“Measuring Gliese 486b’s atmosphere will go a long way towards deciding if we should consider looking for signs of life around red dwarfs. This discovery could change our understanding of planetary atmospheres. We have long known that rocky super-earths with an atmosphere must exist around nearby stars. but until recently we didn’t have the technology to find them.”
The uniqueness of Gliese 486b lies in the fact that: firstly, it is a transit planet, and when it passes in front of its star, part of the starlight penetrates its atmospheric layer and can be studied by transmission spectroscopy; and second, it is located close to the star, and the heat of the star “inflates” the atmosphere, helping astronomers to carry out atmospheric measurements using emission spectroscopy.
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In both cases, scientists use a spectrograph, an instrument that separates light according to its wavelengths to decipher the chemical composition of the atmosphere.
The results of the study are published in the journal Science.