The latest research has shown that the likelihood of the existence of alien life in the universe is much higher than was commonly believed.
Previous attempts to assess the possibility of life on Earth-like planets have failed, since there was only one starting point for such reasoning - the Earth itself. The data obtained from the analysis of fossils made it possible to determine that life began on Earth 25-600 million years after the planet became habitable. However, it is impossible to determine whether the emergence of life was a unique event for our planet, or the same is happening with other similar planets in the universe.
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Statistical analyzes by Charles Lineweaver and Tamara Davis of the University of New South Wales in Sydney suggest that life could have originated on at least a third of Earth-like planets over billions of years. And the latest discoveries, indicating that there are many such planets around stars like the Sun, allow us to say that there may be many inhabited planets in the Universe.
Lineweaver believes that the chances of the birth of life are similar to the chances of winning the lottery: “The fact of such a win on Earth gives us the opportunity to estimate its probability. If we only know that the player won on the third try, we cannot determine the real odds, but we can say that the probability of such a win is more likely one in three than one in a billion."
The scientist is 95 percent sure that the chance of the birth of life in a billion years on a suitable planet for this is at least one in three.
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Planetary systems are primarily to be found near metal-rich stars. Thus, the search for planets where life like Earth exists is greatly simplified, experts say.
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“20% of metal-rich stars have planets - it's amazing,” says Debra Fisher of the University of California, Berkeley. At the congress of the International Astronomical Union, held in Sydney, she announced that this result was obtained after studying more than 750 stars. In this case, "metals" meant all elements, except for hydrogen and helium.
Planets are also composed of relatively heavy elements, so scientists have suggested that they are more likely to occur near metal-rich stars. The new discovery will allow preliminary selection of the most likely candidates for the search for planetary systems, significantly increasing the efficiency of such a search.
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Well, NASA experts recently calculated a star around which planets most likely inhabited by intelligent life can orbit. If the alien planets live somewhere, then, most likely, it is there - in the constellation Gemini, on the planets of the 37th brightest star in this cluster, designated Gem 37.
Astrobiologist Maggie Thornburn, conducting research on stellar systems commissioned by NASA, analyzed about 5,000 stars and eventually compiled a list of 30 on which life is most likely to exist.
In the future, NASA plans to use this list to search for planets like Earth. The ambitious project kicks off in 2013, and by then scientists should be clear about which stars to focus on.
The star Gem 37, which tops Thornburn's list, is close in age to the Sun, but slightly brighter and warmer than our star.
"Similarity" is the main criterion by which Thornburn selected stars. “The longer you look, the more you realize that the vast majority of stars are different from our Sun,” she says.
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The problem of finding planets like Earth is a major challenge for astronomers. Telescopes located on the surface of our planet cannot detect such small cosmic bodies - to date, astronomers have examined about 100 planets, but they are all gas giants, like Jupiter, the largest planet in the solar system. Of course, they are not suitable for life.
NASA specialists plan to search for "earth-like" planets using the most powerful telescopes placed in Earth's orbit. Thornburn's research will help figure out where to target space observatories.
Thornburn does not exclude that adjustments will be made to the list in the future - if other criteria are suddenly discovered that indicate a high probability of the emergence of life in other stellar systems.
Douglas Capone, a biology professor at the University of Southern California, offers a slightly different approach to finding life outside of Earth.
According to Capone, unlike the common view that other planets should first look for liquid water (as the most important condition for life), researchers should focus on finding nitrogen, which makes up 80% of the earth's atmosphere. It is involved in a giant cycle of biochemical reactions driven by bacteria that synthesize nitrogen compounds, which then enter plants and animals, and then into sedimentary rocks, the ocean, and again into the atmosphere. The researcher believes that nitrogen is a much more reliable indicator of the existence of life on the planet at a given time.
The microscopic amount of nitrogen in the atmosphere of Mars, according to the biologist, is a sign of the absence of life (or abundant life) there at the present time and, possibly, a trace of life that existed in the distant past.
As noted by Douglas Capone, if somewhere in the Universe there is life similar to ours, it should be searched for by the nitrogen cycle and, accordingly, by the nitrogen-rich atmosphere: it is on the search for such planets that astronomers should focus.
In addition, according to the scientist, from recent discoveries in this area, one should recall liquid water at Enceladus, where, apparently, there are potential conditions for life.