Are we made up of alien atoms?

Half of all the atoms found in humans came from a galaxy far, far away, a new study suggests.

Astrophysicists at Northwestern University in Chicago have found that up to 50 per cent of the matter that makes up our bodies, planet and the solar system was probably formed a million light years beyond the Milky Way.

Supercomputer simulations suggest it was transported by powerful intergalactic winds made of gas from the explosions of dying stars in distant galaxies.

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"Supernova explosions can fling trillions of tonnes of atoms into space with such ferocity that they escape their home galaxy's gravitational pull and fall towards larger neighbours in enormous clouds that travel at hundreds of kilometres per second," reports Ian Sample, The Guardian's science editor.

Much of the hydrogen and helium that falls into galaxies forms new stars, he adds, while heavier elements become the building blocks for comets and asteroids, planets and life.

"Science is very useful for finding our place in the universe," says lead researcher Daniel Angles-Alcazar. "In some sense we are extragalactic visitors or immigrants in what we think of as our galaxy."

The next step for Angles-Alcazar and his research team is to work with observatories and Hubble Space Telescope astronomers to test out the simulation predictions, Wired reports.