The revelation emerges from computer simulations that reveal how galaxies grow over eons by absorbing huge amounts of material that is blasted out of neighbouring galaxies when stars explode at the end of their lives. These supernovas can fling atoms into space with such force that they escape their home galaxy’s gravitational pull and fall into other galaxies.
While astronomers have long known that elements forged in stars can travel from one galaxy to another, this latest research study is the first to reveal that up to half of the material in the Milky Way could have arrived from smaller galactic neighbours.
The simulations showed that the Milky Way absorbs about one sun’s-worth of extragalactic material every year, the report said.
“Science is very useful for finding our place in the universe,” said Daniel Anglés-Alcázar, an astronomer at Northwestern University in the US. “In some sense we are extragalactic visitors or immigrants in what we think of as our galaxy.”
“The surprising thing is that galactic winds contribute significantly more material than we thought,” said Anglés-Alcázar. “In terms of research in galaxy evolution, we’re very excited about these results. It’s a new mode of galaxy growth we’ve not considered before.”
The simulations showed that elements carried on intergalactic winds could travel a million light years before settling in a new galaxy, according to a report in the Monthly Notices of the Royal Astronomical Society.
Claude-André Faucher-Giguère, another astronomer on the team, said that before their simulations, galaxies were thought to grow primarily by absorbing material left over from the Big Bang. “What we did not anticipate, and what’s the big surprise, is that about half of the atoms that end up in Milky Way-like galaxies come from other galaxies,” he said. “It gives us a sense of how we can come from very far corners of the universe.”
“Our origins are much less local than we thought,” said Faucher-Giguère. “This study gives us a sense of how things around us are connected to distant objects in the sky.”