Simulations reveal that up to half the material in our galaxy arrived from smaller galactic neighbours, as a result of powerful supernova explosions
Nearly half of the atoms that make up our bodies may have formed beyond the Milky Way and travelled to the solar system on intergalactic winds driven by giant exploding stars, astronomers claim.
The dramatic conclusion emerges from computer simulations that reveal how galaxies grow over aeons by absorbing huge amounts of material that is blasted out of neighbouring galaxies when stars explode at the end of their lives.
Powerful supernova explosions can fling trillions of tonnes of atoms into space with such ferocity that they escape their home galaxys gravitational pull and fall towards larger neighbours in enormous clouds that travel at hundreds of kilometres per second.
Astronomers have long known that elements forged in stars can travel from one galaxy to another, but the latest research is the first to reveal that up to half of the material in the Milky Way and similar-sized galaxies can arrive from smaller galactic neighbours.
Much of the hydrogen and helium that falls into galaxies forms new stars, while heavier elements, themselves created in stars and dispersed in the violent detonations, become the raw material for building comets and asteroids, planets and life.
Science is very useful for finding our place in the universe, said Daniel Angls-Alczar, an astronomer at Northwestern University in Evanston, Illinois. In some sense we are extragalactic visitors or immigrants in what we think of as our galaxy.
The researchers ran supercomputer simulations to watch what happened as galaxies evolved over billions of years. They noticed that as stars exploded in smaller galaxies, the blasts ejected clouds of elements that fell into neighbouring, larger galaxies. The Milky Way absorbs about one suns-worth of extragalactic material every year.
The surprising thing is that galactic winds contribute significantly more material than we thought, said Angls-Alczar. In terms of research in galaxy evolution, were very excited about these results. Its a new mode of galaxy growth weve 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.