Planets in our galaxy.
At least 3.5% of the stars in our Galaxy may have Earth-like planets made up of solid rock. This is about a billion worlds, a small part of which can be inhabited by living organisms, according to a report by scientists presented on Tuesday at the Annual Meeting of the Royal Astronomical Society in the UK.
The discovery of planets outside the solar system is still an extraordinary astronomical task, and the identification of small planets comparable in their parameters to the Earth is a task that has not been solved at all to date. Despite the fact that astronomers have already discovered several so – called super – earths in space-planets that have a similar structure to the Earth, but have a large mass and size-astronomers are still several decades away from the mass discovery of small planets by improving astronomical methods and tools. However, a team of scientists led by Jay Farihi from the University of Leicester in the UK has shown that our Galaxy, the Milky Way, can contain a huge number of planets similar in structure to Earth. At the same time, some of them, based on purely statistical considerations, must inevitably meet the conditions necessary for the emergence of life. In their work, the scientists drew attention to the spectrum of the glow of a special class of stars – white dwarfs, which, according to modern astronomers, are one of the final stages of the evolution of any star similar to our Sun in mass. In the course of their evolution, such stars first pass through the red giant stage, during which their diameter can increase by 200 times. This is due to the fact that in the bowels of stars, the hydrogen fuel that has supported their glow for billions of years ends, the core begins to shrink, additionally warm up and “ignite” thermonuclear reactions in the outer layers of the star, which leads to expansion. This expansion is so large that it goes beyond the orbits of the planets closest to the star, which in the case of the Solar System are small planets, including the Earth. As a result, the substance of the planet passes to the star. Gradually, the “swollen” star begins to shrink into another form – the so-called white dwarf. The analysis of the chemical composition of this atmosphere is easy to carry out, which in their work was done by scientists who showed that of the 146 white dwarfs they studied, 109 showed signs that once in the past, in the state of red giants, they absorbed their planets consisting of solid rocks. Extrapolating this data to the entire Milky Way allowed scientists to establish that at least about a billion earth-like planets may exist in our Galaxy at the same time, some of which may be inhabited by some form of life. According to planetary scientist Jonathan Fortney, quoted by Science NOW, this work of astronomers shows that the formation of Earth-like planets is a much more common process than previously thought, and therefore there may be significantly more than a billion such planets in the Milky Way.