Tatiana Pichugina. Scientists tend to believe that the area of the milky Way where the Solar system came into being, is not a random place. In galaxies, as in the vicinity of stars, there are also the habitable zone. Importantly, there have developed suitable conditions for the development of complex life forms.
The sun in the sleeve
Astronomers have discovered some four thousand planets in other star systems of the Galaxy are a couple hundred Earth-like. Is it possible to find earth-like worlds more precisely? It turns out that experts have been trying to answer this question.
Stars consist mainly of hydrogen and helium. The earth and other rock planets, by contrast, concentrate the heavier chemical elements — oxygen, silicon, aluminum, iron, carbon, radioactive isotopes. Where did they come from? Source scientists believe the aging star exploded and especially very heavy bodies, forming the brightest objects — supernovae.
It turns out that the cloud of material from which the Solar system formed, was somewhere near the old stars and supernovae and there was enriched with “metals” — as in astrophysics call everything heavier than helium.
There was a hypothesis that 4.6 billion years ago, “the germ” of the Solar system visited a factory of chemical elements. This is not the center of the milky way, where a lot of old exploding stars, and young and active. After all, our star is about eight kiloparsecs — and this is a terribly long distance.
Most likely, protocolname the cloud passed through one of two spiral arms — areas where focus stars, interstellar gas and dust. In the disk of the Galaxy they move with different speeds: the closer to the centre run faster on the distant frontiers and slower entering of density waves, then leaving them. But there is such an orbit, where the angular velocity of galactic objects and this ripples coincide and space matter is always on the crest of a wave or, conversely, between the waves. Talking about corotational circle.
That the Sun was born in this area, first drew attention to the Soviet astrophysicist Leonid Marochnik. There protocolname cloud filled “metals” and tested the compression, a necessary condition for the birth of a star.
Space is a dangerous place to live. Here occur the phenomenon, which will not save any atmosphere or planetary magnetic field. For example, a supernova explosion is a powerful source of shock waves, heat and hard electromagnetic radiation — literally sterilizes the surrounding area within a radius of several parsecs. With us this has not yet happened.
Scientists from the University of Trieste (Italy) have estimatedthat the maximum number of stars, where possible inhabited worlds are concentrated in the milky way at a distance of eight kiloparsec from the centre — just where in the Solar system.
Another danger to all living things — gamma ray bursts. It is a powerful emission of hard electromagnetic radiation in the explosion of supernovae or the merger of two neutron stars. These events may be responsible for mass extinction of fauna on Earth in past epochs.
The source of the hard ionizing radiation and serve as the nuclei of galaxies in the phase of activity. The milky way is this period occurred approximately eight billion years ago and lasted for about a billion years. If we assume that in the Galaxy at this time was inhabited worlds, then the active nucleus Sgr A* sterilized them. Planet lost the atmosphere, even at a distance of a few parsecs, say researchers from the University of Rome tor Vergata.
The threat comes from large comets. Collision with these objects can result in earth-like planets disaster. It is believed that the ice bodies are concentrated on the outskirts of the Solar system, the hypothetical Oort cloud. Throw them out to the center capable of passing a single star. This happens rarely, since our system is located in a sparsely populated region.
It would seem that the conclusion is obvious: for the origin of life star system should be located away from potential sources of hard radiation. But not on the edge of the Galaxy, for example, in halo, as there is little “metals”, and somewhere in the middle. But Michael Gouinlock from MIT (USA) questioned this. According to his model of the milky way, in the inner parts of the Galaxy are much more likely to meet a potentially habitable star system than on the periphery, despite the fact that there often there is a catastrophic supernova explosions. The first biosphere could arise in the Galaxy long before the Solar system over ten billion years ago, while avoiding death from gamma-ray bursts or the birth of a supernova.