We are all made of star stuff and some of that stuff took a long journey to get here. According to new research, galaxies exchange copious amounts of material, and half of the material that makes up the Milky Way might have originated in another galaxy.
Researchers from Northwestern University have run a supercomputer simulation and discovered that the intergalactic transfer of material is a major player when it comes to galaxies getting new material. The study, published in the Monthly Notices of the Royal Astronomical Society, suggests that strong galactic winds are responsible for launching it into space.
Galactic winds are generated by supernova explosions and they move at several hundred kilometers per second, so the intergalactic transfer takes billion of years. The simulation showed that material could have moved from up to a million light-years away and that the material goes from the smaller galaxies in a system to the bigger ones, like the Milky Way.
“This study transforms our understanding of how galaxies formed from the Big Bang,” co-author Professor Claude-André Faucher-Giguère, from the Weinberg College of Arts and Sciences, said in a statement. “What this new mode implies is that up to one-half of the atoms around us – including in the solar system, on Earth and in each one of us – comes not from our own galaxy but from other galaxies, up to one million light-years away.”
The findings from the simulation are extremely intriguing and provide a series of observable predictions. The team plans to collaborate with other astronomers and use telescopes like Hubble to see if intergalactic transfer actually happens and if it matches the expectations from the simulations.
“Given how much of the matter out of which we formed may have come from other galaxies, we could consider ourselves space travelers or extragalactic immigrants,” added Daniel Anglés-Alcázar, from Northwestern’s astrophysics center, who led the study. “It is likely that much of the Milky Way’s matter was in other galaxies before it was kicked out by a powerful wind, traveled across intergalactic space and eventually found its new home in the Milky Way.”
Galaxy evolution is a messy business. Galaxies collide with each other, merge, and throw each other around. Intergalactic transfer might soon be considered just as important in the making of galaxies.

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