Astronomers have discovered an atmosphere around an exoplanet in the constellation Sails. At the moment, it is the most Earth-like exoplanet for which it was possible to confirm the presence of an atmosphere.
For the first time, it was possible to detect the atmosphere of a planet outside the solar system in 2001. It was found near the planet HD 209458 b, also known under the unofficial name Osiris. It is located in the constellation Pegasus, 153 light years from the Sun. By its type, Osiris is "hot Jupiter", that is, a gas planet with a mass close to that of Jupiter, but located much closer to its star than Jupiter is to the Sun. Osiris has a radius of about 100,000 km (1.35 Jupiter's radii), a mass of 1.31024 tons (0.69 Jupiter's masses), and the distance to the star is only 0.047 astronomical units (much less than from the Sun to Mercury). A year on it lasts three and a half Earth days, and the temperature reaches a thousand degrees Celsius.
The discovery of the atmosphere was made possible by the fact that HD 209458 b became the first planet for which its own spectrum of radiation was obtained, extracted from the radiation of its star. Sodium absorption lines were found in this spectrum of the steel. In further studies, assumptions were made about the extent, structure and temperature of its atmosphere. The atmosphere begins at a distance of 3.1 times the radius of Jupiter from the center of the planet. It contains hydrogen, oxygen, carbon, carbon dioxide and methane, as well as water vapor. The temperature of the atmosphere reaches 10 thousand Kelvin. It is very likely that the planet, due to the strong heating of the upper atmosphere by the radiation of the star, constantly loses atmospheric gases, since hydrogen atoms are accelerated to the second cosmic velocity. It is with this that the choice for the planet of the name Osiris is connected,since this Egyptian god was once chopped to pieces by the god Set. The planet Osiris is estimated to be losing between one hundred and eight hundred million kilograms of hydrogen per second. For about five billion years of existence, the planet could have lost up to 7% of its mass, but it is likely that the loss of hydrogen could be restrained by the Osiris magnetosphere. Perhaps the atmosphere of Osiris is typical of planets orbiting stars similar to the Sun, at a distance of less than 0.1 astronomical units.orbiting stars similar to the Sun, at a distance of less than 0.1 astronomical units.orbiting stars similar to the Sun, at a distance of less than 0.1 astronomical units.
Soon water vapor, hydrogen monoxide and dioxide and methane were found in the atmosphere of another hot Jupiter - HD 189733 b. In 2013, traces of water were found in the atmospheres of several planets: HD 209458 b, XO-1b, WASP-12b, WASP-17b and WASP-19b. The overwhelming majority of exoplanets on which it was possible to confirm the presence of an atmosphere are hot Jupiters and hot neptunes. The presence and composition of these atmospheres can be judged from two types of observations. First, by the refraction of light from a star in the atmosphere when an exoplanet passes in front of the star's disk. Secondly, according to the direct spectrum of the planet's radiation, which is obtained by comparing the spectra of the parent star together with the planet and those obtained when the planet is hidden behind the star.
In February 2016, astronomers reported on the determination of the composition of the atmosphere of the planet 55 Cancer e (Jansen). It belongs to the class of super-earths - planets whose mass is greater than that of our planet, but does not reach the parameters of gas giants. For Jansen, this figure is 8.63 ± 0.35 Earth masses. The composition of the planet's atmosphere was detected by changing the spectrum of its parent star - 55 Cancer - during the so-called transits, that is, moments when, from the point of view of an earthly observer, the planet passes in front of the star's disk. During this passage, part of the star's light passes through the planetary atmosphere, while certain wavelengths are absorbed by the gases of the atmosphere, which makes it possible to determine its chemical composition. The observations were made with the Hubble Space Telescope's wide-angle camera. In the atmosphere of the planet Jansen, as it turned out,contains hydrogen, helium and hydrogen cyanide.
In December last year, scientists for the first time managed to determine the weather conditions in the atmosphere of one of the exoplanets. They used data on the planet HAT-P-7 b, in the constellation Cygnus, collected by the Kepler space telescope over four years. HAT-P-7 b refers to hot Jupiters. Its mass is 1.776 Jupiter's masses (16 times that of Earth), and its diameter is 1.363 times the diameter of Jupiter. This planet is separated from Earth by 1,044 light years. HAT-P-7 b belongs to the "hot Jupiters" class. It revolves around its star with a period of 2.2 days. By detecting a change in the amount of light reflected by the atmosphere of HAT-P-7 b, the scientists noted a dramatic change in the position of its brightest region. This, in their opinion, indicates very strong winds that affect the clouds in the atmosphere. “Strong winds blow around the planet, moving clouds from the night side to the day side,- says one of the authors of the work, David Armstrong (David Armstrong). "The speed of the wind changes so dramatically that it creates huge cloud formations that grow and then disappear."
The current study focused on the planet GJ 1132b (Gliese 1132 b), orbiting one of the stars in the constellation Sails. It was observed by employees of the University of Keele, the Max Planck Institute for Astronomy and the Tor Vergata University of Rome using the 2.2-meter telescope of the European Southern Observatory in La Silla (Chile).
The planet orbits the red dwarf Gliese 1132 at a distance of 39 light years from us. Its opening was announced in May 2015, and official confirmation followed in November of the same year. Its mass is 1.6 Earth masses, its radius is 1.2 Earth's radius. The distance to the star is about 225 million kilometers (from the Earth to the Sun 149.6 million), the orbital period is 1.6 days. The planet receives 19 times more radiation from its star than the Earth from the Sun, so the temperature on it is higher than on Venus, possibly at the surface it exceeds 500 ° C.
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The observations were carried out during nine transits of planet GJ 1132b in seven different bands: two in the infrared and seven in the visible parts of the spectrum. For each range, the apparent size of the planet was estimated. As a result, the researchers found that in one of the infrared ranges, its diameter significantly exceeds the data for the rest of the range. This allows us to conclude that there is a gas envelope around the planet, which is opaque for light waves of a given wavelength and transparent for everyone else. Further simulations carried out at the University of Cambridge and the Max Planck Institute for Astronomy have shown that such effects are well explained by the presence of water vapor and methane in the atmosphere.
It was previously believed that the atmospheres of planets orbiting red dwarfs cannot exist for a long time, since these stars are too active and their outbursts will inevitably lead to the destruction of these atmospheres. The new results are encouraging, as the atmosphere of GJ 1132b appears to have existed for billions of years. Since red dwarfs are so common in the Universe, the presence of atmospheres in their stars increases the chances of conditions for extraterrestrial life.
The work of scientists was published by the Astronomical Journal.