Why are there so few potentially habitable exoplanets? Blame it on the red dwarfs

One of the most amazing events in modernAstronomy has become the boom of discoveries of various exoplanets. Hundreds of new worlds located outside the solar system, quite possibly very similar to the Earth, waiting for, when they open life. However, the results of a new study by the University of Vienna and the Space Research Institute (IWF) of the Austrian Academy of Sciences (ÖAW) in Graz, presented in the journal Astronomy & Astrophysics Letters (press release published by Science Daily), suggest that this joyful event overshadows One very sad fact: the atmosphere of these young worlds is most likely not able to withstand the radiation of the stars around which they rotate.

For life, at least for the one that willlike the earth, the stars will always be crucial: they create habitable areas with their radiation. And if the planets rotate in such a region, then the temperatures on its surface remain in the range in which the water on them can exist in a liquid state. As for living beings, whose life may be based on other principles, in this respect, science has not yet had any clear ideas. But the power of stellar radiation can also be fatal for places suitable or potentially liveable - when very active stars literally blow away the atmospheres of such planets.

So many exoplanets revolve around socalled M-dwarfs, also known as red dwarfs. Since the stars of this type are much smaller and colder than our Sun, the researchers simply ignored them for a very long time. Only recently, they became the center of attention for researchers searching for potential extraterrestrial life. For example, Proxima Centauri, the star nearest to our solar system, belongs to the M-class of stars. Its size is only 1/8 the size of our luminary.

The main problem with these starslies in the fact that their evolution is markedly different from the evolution of stars like our sun. At one time, especially in the first hundreds of millions of years of its existence, our star also was distinguished by its “violent disposition”, characterized by high activity. But then it reduced the production of high-energy ultraviolet and x-rays. Unlike stars like our Sun, M-dwarfs can maintain a very high level of radiation for several billion years.

And these radiations have dramatic consequences.for the atmospheres of the planets, especially those that revolve around such stars in close orbits, in the so-called "habitable zone". The continuous active radiation of the parent star heats the gases in the upper layers of the atmosphere of such planets to several hundred degrees Celsius, leading to their evaporation.

Scientists from the University of Vienna with theircolleagues from other scientific institutions made calculations how quickly the process of atmospheric extinction may occur in planets that are close to red dwarfs. Modeling has shown that for an earth-like planet orbiting a very active star, this will happen disastrously quickly - in less than a million years. On an astronomical scale - almost instantly, the researchers say.

As our Sun calmed down relativelyEarly, after a few hundred million years, our planet had the opportunity to create its own nitrogen atmosphere, which protected its surface from the effects of the radiation of a star. In turn, the new calculations show that the planets in the inhabited zones of red dwarfs can remain without this protective shell for much longer — billions of years.

Summing up, the researchers say thatsuch results also reflect the likelihood of how life could be formed and maintained on planets orbiting M-class stars. Prospects, as you probably already understood, are not very bright.

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