Why do so few potentially habitable exoplanets? Blame it on the red dwarfs
One of the most amazing events in modern astronomy has become a boom of various discoveries of exoplanets. Hundreds of new worlds outside the solar system, it is possible, it is very similar to the Earth, waiting, and when they discover life. However, results of a new study conducted by the University of Vienna and the Space Research Institute (IWF) of the Austrian Academy of Sciences (ÖAW) in Graz, presented in Astronomy & Astrophysics Letters Journal (press release published on the site Science Daily), say that it is a joyful event overshadows a very sad fact: the atmosphere of these young worlds, most likely not able to withstand the radiation of the stars around which they orbit.
to life, at least for the one that will be like the earth, the stars will always be critical: they create through their radiation habitable area. And if the planet rotate in such a region, then its surface temperature are within a range in which the water in them can exist in a liquid state. With regard to living beings, whose lives may be based on different principles, in this respect, science has not yet been any clear ideas. But the radiation power of the stars can also be fatal for places suitable or potentially suitable for life - when a very active stars literally blow away the atmosphere of such planets. Too many extrasolar planets revolve around the so-called M-dwarfs, also known as red dwarfs. As the stars of this type is much smaller and cooler than our Sun, researchers them for a long time simply ignored. Only recently they were the focus of the researchers involved in the search for potential extraterrestrial life. For example, the closest to our solar system, Proxima Centauri star refers to the M-class stars. Its size is only 1/8 the size of our star.
The main problem with these stars is that their evolution is markedly different from the evolution of stars like our sun. In due time, particularly in the first few hundred million years of its existence, our star also differed "violent temper", characterized by high activity. But then it has 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 a few billion years.
And these radiations have dramatic consequences for the atmospheres of the planets, especially those that revolve around such stars on close orbits in the so-called "habitable zone". Prolonged active radiation parent star strongly heats the gases in the upper atmosphere such planets to several hundred degrees Celsius, causing them to evaporate. Scientists from the University of Vienna with their colleagues from other research institutions have produced estimates of how fast the process is the disappearance of the atmospheres of the planets, close to the red dwarfs. The simulation showed that for Earth-like planets orbiting very active star, it will be catastrophic speed - less than a million years. In astronomical scales - almost instantaneously, the researchers say.
As our sun has calmed down relatively early, after only a few hundred million years of our planet have the opportunity to create a nitrogen atmosphere, which protects the surface from exposure to light radiation. New calculations show that the planets that are in the habitable zone of red dwarfs, can remain without this containment for much longer, in turn - for billions of years.
Summing up, the researchers say that these results reflect the probability of being on the planets orbiting the M-class stars would form and maintain life. Perspective, as you probably already realize, is not very optimistic.
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