The Milky Way never ceases to present surprises. "Elements of life", ultrafast stars and unusual clusters of luminaries, unknown components - all this astronomers have discovered in our home galaxy only in the last couple of years.
However, the Milky Way still has many secrets, and one of the most interesting, perhaps, was unraveled by American astrophysicists in the course of a new study. It turns out that half of all the matter in the Milky Way is of extragalactic origin, that is, it comes from other, distant galaxies, which are up to a million light years away from us.
To understand this, the researchers were helped by computer models that reveal the history of the origin of galaxies. Simulations have shown that supernova explosions are pushing huge amounts of gas from native galaxies, and powerful winds carry them over long distances.
This intergalactic transport is a new phenomenon for astrophysicists. To study it to understand the evolutionary history of galaxies is possible only through modeling.
“Considering how much matter was brought in from the outside, we may well consider ourselves space travelers or intergalactic immigrants. Probably, most of the matter in the Milky Way was originally located in other galaxies, before powerful winds “knocked out” it. She traveled through intergalactic space and eventually found herself a new 'home' in our galaxy,”says head of the research team Daniel Anglés-Alcázar of the Center for Interdisciplinary Research in Astrophysics at Northwestern University in the United States.
It would seem that galactic winds, which have a speed of several hundred kilometers per second, should transport matter incredibly quickly. However, do not forget that galaxies are located at a huge distance from each other, so the process of intergalactic transfer can take billions of years.
To calculate and study such processes, a team led by Professor Claude-André Faucher-Giguère created realistic three-dimensional models of galaxies, which can be used to trace the history of the formation of the Milky Way - from the Big Bang to the present day. The Angles-Alcazar group then developed algorithms to determine how and how much matter is carried by winds into galaxies.
After closely tracking the flows of matter in simulations, the researchers found that gas moves from smaller galaxies to larger ones, where it is then involved in star formation. In large galaxies, the proportion of such "incoming matter" is up to 50%. For example, into the Milky Way, most of the alien matter was probably transferred from the neighboring galaxies - the Large and Small Magellanic Clouds.
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“This study completely changes our understanding of how galaxies formed. Up to half of the atoms around us - and in the solar system in general - are of extragalactic origin,”notes Fauche-Zhiguere.
“In our models, we were able to trace the origin of stars in galaxies similar to the Milky Way, and determine whether the star was formed from the matter of the 'native' galaxy or from gas that was previously in another galaxy,” adds Angles-Alcazar.
According to the authors of the work, their results will open a new direction in research. First of all, the theory of intergalactic transport will have to be tested by practical astronomers working with ground and space observatories.
“Our origins are much less local than we previously thought. This study gives an idea of how everything around us is related to distant objects in the sky,”concludes Faucher-Giguere.
A scientific article following the research was published in the Monthly Notices of the Royal Astronomical Society.