Parent star and distance to it
Life on other planets may be unlike anything on Earth -
The habitable zone, or the habitable zone, isa conditional area in space, determined from the calculation that the conditions on the surface of the planets in it will be close to the conditions on Earth and will ensure the existence of water in the liquid phase.
Earth-sized planets in wide orbitsAround stars like the Sun, it is much more difficult to detect than gas giants around red dwarfs. Even if there is a rocky world near them, such stars have a habit that is dangerous for any life, especially at a young age. The fact is that powerful flashes erupt on their surface. They can simply sterilize closely orbiting planets where life has just begun to emerge.
Since our Sun has fed life on Earth almost4 billion years old, conventional wisdom suggests that such stars will be prime candidates for other potentially habitable worlds. However, yellow G-type stars like our Sun are rare in our galaxy.
Stars that are slightly cooler and less brightthan our Sun, orange dwarfs (or K-dwarfs) are considered by some scientists to be potentially better for advanced life. They can burn continuously for tens of billions of years. This opens up a vast time frame for biological evolution, allowing for an infinite number of experiments to produce sustainable life forms. And for every star like our Sun, there are three times as many orange dwarfs in the Milky Way.
K dwarfs are notable because they haveintermediate properties of rarer, brighter but short-lived solar-type stars (G-class) and numerous red dwarfs (M-class). K stars are the best candidates for a host star for a habitable planet.
However, given that there are not so many of them, scientistsplan to study worlds around M-dwarfs. The first opportunity to use observations to characterize small exoplanetary environments and perhaps search for biosignatures is expected with the launch of the James Webb Space Telescope (JWST). He will just observe small planets orbiting red dwarfs. They are smaller, cooler, redder, but more numerous than stars like our Sun.
Water is the source of life
Water plays an extremely important role inthe global circulation of matter and energy, the emergence and maintenance of life on Earth, the chemical structure of living organisms, the formation of climate and weather. It is the most important substance for all living beings on our planet. Therefore, scientists are sure that if there is life somewhere in space, then it requires water.
Planet K2-18b orbits its dim red host star in the illustration. This exoplanet — the first of its kind to contain water vapor in its atmosphere.
By the way, NASA's new Perseverance mission will belook for signs of ancient microbial life, study the geology and climate of the planet, collect samples of rocks and sediments. It is worth noting that the rover landed in the Jezero Crater. This is an impact crater on Mars, in the west of the Isis Planitia, near the eastern edge of Syrtis Major, with a diameter of about 49 km. Scientists are sure that the crater was once filled with water; Dry river channels flow into it, one of which forms a pronounced delta. In addition, the crater contains clay deposits formed under the influence of water.
Earth with 71% of its surface covered by wateroceans, is currently the only known planet in the solar system containing liquid water. There is scientific evidence that on some satellites of the giant planets (Jupiter, Saturn, Uranus and Neptune) water may be under a thick crust of ice covering heavenly body. However, there is currently no clear evidence of the presence of liquid water in the solar system, except on Earth. Oceans and water may be present in other star systems and/or on their planets and other celestial bodies in their orbit. For example, water vapor was discovered in 2007 in a protoplanetary disk at 1 AU. e. from the young star MWC 480.
In 2019, astronomers using the dataHubble Space Telescope announced the discovery of water vapor in the atmosphere of a planet the size of Earth. Although this exoplanet orbits a star that is smaller than our Sun, it falls within the star's habitable zone.
The discovery was the result of many years of observationbehind the exoplanet K2-18b, a super-Earth, which is about 111 light-years from our solar system. It was discovered in 2015 by NASA's Kepler spacecraft.
Biosignatures and among them a new gas
Today, the vast majorityexoplanets discovered and confirmed by indirect methods. Only in rare cases have astronomers been able to obtain real radiation spectra that allow them to accurately determine their chemical composition. However, this will change as next-generation instruments such as the James Webb Space Telescope (JWST) or the Nancy Grace Observatory (100 times more powerful than its predecessor, Hubble) go into space.
In simple words, these uniqueThe devices will be able to observe our Universe at longer wavelengths, in the near and mid-infrared, and with significantly greater sensitivity than currently operating devices. Biosignatures include chemical signatures associated with life and a biological process, and also indicate favorable conditions for it. Previously, such markers were considered oxygen and carbon dioxide, which are produced by living organisms on the Earth, water and methane released during the decomposition of organic substances, as well as some by-products (hydrogen sulfide, sulfur dioxide, carbon monoxide, hydrogen gas, and so on ). However, all this could accumulate on a lifeless planet. But isoprene is an almost unique, rare compound. And it is produced by a huge number of diverse life forms (from bacteria to plants and animals), evolutionarily distant from each other.
According to researchers’ calculations, “the originalplanet" (on which life begins to emerge) must necessarily have a large amount of isoprene in its atmosphere. This was the case on Earth between four and 2.5 billion years ago, when single-celled organisms were the only form of life and photosynthetic cyanobacteria slowly created an oxygen atmosphere around the Earth. So now the search will focus on this compound, reports Universe Today.
Of course, research will face a whole host ofcomplexities. It is not even known whether this will lead to the discovery of extraterrestrial life during the 21st century. But one thing is clear. In the coming years, astronomers will study in detail the atmospheres of thousands of exoplanets and will have an exhaustive list of planets with the most accurate biosignatures, which they can use to guide them in their search for specific traces of life throughout the galaxy.
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