See the scattering of stars in the black night sky - they all contain amazing worlds like our solar system. By the most conservative estimates, the Milky Way galaxy contains more than a hundred billion planets, some of which may be like Earth. New information about "alien" planets - exoplanets - was discovered by the Kepler space telescope, which explores the constellations in anticipation of the moment when the distant planet will be in front of its star. The orbital observatory was launched in May 2009 specifically to search for exoplanets, but four years later it failed. After many attempts to return the telescope to work, NASA in August 2013 was forced to decommission the observatory from its "space fleet". Nevertheless, over the years of observations, "Kepler" received so many unique data that it will take several more years to study them. NASA is already preparing to launch in 2017 Kepler's successor, the TESS telescope.
Super-Earths in the Goldilocks Belt
Today astronomers have identified nearly 600 new worlds out of 3,500 candidates for the title of "exoplanet". It is believed that among these celestial bodies at least 90% may be "true planets", and the rest - double stars that have not grown to stellar size "brown dwarfs" and clusters of large asteroids.
Most of the new planetary candidates are gas giants like Jupiter or Saturn, as well as super-earths, rocky planets several times our size.
Naturally, not all planets fall into the line of sight of Kepler and other telescopes. Their number is estimated at only 1-10%.
To be sure to identify an exoplanet, it must be repeatedly fixed on the disk of its star. It is clear that most often it is located close to its sun, because then its year will last only a few Earth days or weeks, so astronomers will be able to repeat the observations many times. Such planets in the form of hot gas balls often turn out to be "hot Jupiters", and every sixth is like a flaming super-earth covered with seas of lava.
Of course, in such conditions, the protein life of our type cannot exist, but among the hundreds of inhospitable bodies there are also pleasant exceptions. So far, more than a hundred terrestrial planets have been identified, located in the so-called habitable zone, or the Goldilocks belt. This fairy-tale character was guided by the principle "no more, no less." So for the rare planets included in the "zone of life", the temperature should be within the limits of the existence of liquid water. Moreover, 24 of this number have a radius of less than two radii of the Earth.
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However, so far only one of these planets has the main features of the Earth's twin: it is located in the Goldilocks zone, is close to Earth's dimensions and is part of a yellow dwarf system similar to the Sun.
In the world of red dwarfs
However, astrobiologists, persistently searching for extraterrestrial life, are not discouraged. Most of the stars in our galaxy are small, cool and dim red dwarfs. According to modern data, red dwarfs, being about half the size and colder than the Sun, account for at least three quarters of the "stellar population" of the Milky Way.
Around these "solar cousins" orbit miniature systems the size of the orbit of Mercury, and they also have their own Goldilocks belts.
Astrophysicists at the University of California at Berkeley have even compiled a special computer program TERRA, with which they have identified a dozen terrestrial twins. All of them are close to their zones of life in small red luminaries. All this greatly increases the chances of the presence of extraterrestrial centers of life in our galaxy.
Previously, it was thought that red dwarfs, in the vicinity of which Earth-like planets were found, are very calm stars, and on their surface there are rarely flares accompanied by plasma ejections.
As it turned out, in fact, such luminaries are even more active than the Sun. On their surface, powerful cataclysms are constantly occurring, generating hurricane gusts of "stellar wind" that can overcome even the powerful magnetic shield of the Earth.
However, many of Earth's twins can pay a very high price for being close to their star. Radiation streams from frequent flares on the surface of red dwarfs can literally "lick off" part of the planet's atmosphere, making these worlds uninhabitable. In this case, the danger of coronal ejections is enhanced by the fact that a weakened atmosphere will poorly protect the surface from charged particles of hard ultraviolet radiation and X-rays of the "stellar wind".
In addition, there is a danger of suppression of magnetospheres of potentially habitable planets by the strongest magnetic field of red dwarfs.
Broken magnetic shield
Astronomers have long suspected that many red dwarfs possess powerful magnetic fields that can easily pierce the magnetic shield surrounding potentially habitable planets. To prove this, a virtual world was built in which our planet revolves near a similar star in a very close orbit in the "life zone".
It turned out that very often the dwarf's magnetic field not only strongly deforms the Earth's magnetosphere, but even drives it under the planet's surface. According to this scenario, in just a few million years, we would have no air or water, and the entire surface would be scorched by cosmic radiation. Two interesting conclusions follow from this. The search for life in red dwarf systems can be completely futile, and this is another explanation for the "great silence of the cosmos."
However, perhaps we can not find extraterrestrial intelligence because our planet was born too early …
The bleak fate of the firstborn
Analyzing data obtained with the Kepler and Hubble telescopes, astronomers have found that the process of star formation in the Milky Way has slowed significantly. This is due to the growing shortage of building materials in the form of dust and gas clouds. Nevertheless, in our galaxy there is still a lot of material for the birth of stars and planetary systems. Moreover, after a few billion years, our stellar island will collide with the giant galaxy Andromeda Nebula, which will cause a colossal burst of star formation.
Against this background of future galactic evolution, the sensational news recently sounded that four billion years ago, at the time of the emergence of the solar system, only a tenth of potentially habitable planets existed.
Considering that it took several hundred million years for the birth of the simplest microorganisms on our planet, and for several billion years more advanced forms of life were formed, it is highly likely that intelligent aliens will appear only after the extinction of the Sun.
Maybe here lies the solution to the intriguing Fermi paradox, which was once formulated by an outstanding physicist: where are these extraterrestrials? Or does it make sense to look for answers on our planet?
Extremophiles on Earth and in space
The more we are convinced of the uniqueness of our place in the Universe, the more often the question arises: can life exist and develop in worlds that are completely different from ours?
"Tardigrades" are able to exist in the vacuum of space.
The answer to this question is given by the existence on our planet of amazing organisms - extremophiles. They got their name for their ability to survive in extreme temperatures, a toxic environment, and even an airless space. Marine biologists have found similar creatures in underground geysers - "sea smokers". There they thrive under tremendous pressure in the absence of oxygen at the very edge of the hot volcanic vents. Their "colleagues" are found in salt mountain lakes, hot deserts and subglacial waters of Antarctica. There are even microorganisms "tardigrades" that carry space vacuum. It turns out that even in a radiation environment near red dwarfs, some "extreme microbes" can appear.
An acid lake located in Yellowstone. Red bloom - acidophilic bacteria.
Academic evolutionary biology believes that life on Earth originated from chemical reactions in a "warm shallow body of water", permeated by streams of ultraviolet radiation and ozone from raging "lightning storms". On the other hand, astrobiologists know that the chemical building blocks of life are found in other worlds as well. For example, they were noticed in the gas and dust nebulae and satellite systems of our gas giants. This, of course, is still far from a "full life", but the first step towards it.
The "standard" theory of the origin of life on Earth has recently been hit hard by…. geologists. It turns out that the first organisms are much older than previously thought, and formed in a completely unfavorable environment of a methane atmosphere and boiling magma pouring out from thousands of volcanoes. This makes many biologists wonder about the old panspermia hypothesis. According to it, the first microorganisms originated somewhere else, say, on Mars, and came to Earth in the core of meteorites. Perhaps the ancient bacteria had to make a longer journey in cometary nuclei that arrived from other stellar systems.
But if this is so, then the paths of "cosmic evolution" can lead us to "brothers in origin" who have drawn the "seeds of life" from the same source as we …
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