About half of the matter in stars and the entire Milky Way as a whole got into it from neighboring galaxies, which indicates a possible extragalactic origin of the Earth and the solar system, according to an article published in the journal MNRAS.
“Given how much of the Milky Way matter that we are made of could have come from other galaxies, we can consider ourselves space travelers or intergalactic migrants. In other words, the history of the origin of the solar system and humanity may be much less local than we believe today,”says Daniel Angles-Alcazar of Northwestern University in Chicago (USA).
The Milky Way sits in an intergalactic void, accompanied by a retinue of dwarf galaxies, most of which are invisible due to their extreme dimness. Scientists believe that many of these dwarfs periodically approach our Galaxy, the final traces of which are the so-called stellar streams.
They look like ribbons of stars that are not connected to each other by gravity, revolving around the center of the Milky Way above and below its disk, which contains the Earth, the Sun and almost all other stars. Stellar streams, according to astronomers, are the remnants of globular clusters or dwarf galaxies that were torn apart or absorbed by the Milky Way in the distant past.
Observing one of the most noticeable stellar streams - the so-called Ring of the Unicorn, astronomers have found that during these apocalyptic events, the Milky Way "steals" almost all dark matter from the galaxies it ruptures. As a result, they disintegrate and turn into ribbons that can be seen in the night sky above the disk of the Galaxy.
Angles-Alcazar and his colleagues decided to find out how often the Milky Way experienced such collisions and how much of its matter could be the remains of such torn galaxies. To do this, scientists have created a computer model of the Galaxy and its immediate surroundings, which makes it possible to trace how they will interact over several billion years.
This model, according to scientists, took into account not only the movement of the galaxies themselves, but also their interaction with the gas reserves in the intergalactic medium, as well as how they generate the so-called quasar winds - powerful streams of gas moving from relatively dense regions of space to relatively empty regions under the influence of radiation from supermassive black holes and supernova explosions.
As these calculations showed, "eating" other galaxies is not the main source of matter, which the Milky Way "stole" or continues to "steal" from its neighbors - no less amount of gas and dust got into it along with quasar winds that left hundreds of neighboring galaxies. million or several billion years ago. In total, they account for about half of the mass of large galaxies, as calculations by Angles-Alcazar and his team show.
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“Such conclusions are radically changing our understanding of how galaxies were formed after the Big Bang. If the Galaxy grew in this way, then about half of the atoms that surround us, including the entire solar system and the Earth, once belonged not to the Milky Way, but to distant galaxies a million light-years from us, concludes Claude-André Foche-Giguert (Claude -André Faucher-Giguère), a colleague of Angles-Alcazar.