We Are Indeed Made of Stars: Half of the Atoms in the Milky Way Originated in Distant Galaxies

It seems that the idea of us being made of stars is not just a romantic notion after all. We are closer to the stars than you could imagine, and a recent study has found some evidence for that.

Many of us feel a mysterious connection with the universe and are fascinated with the stars in the night sky. It may feel like being homesick for a distant place you’ve never been to, somewhere far away from our planet and galaxy. What if this unexplained longing for the stars has quite a logical explanation?

According to a new study, nearly half the matter in our galaxy, which includes everything it contains – stars, planets and eventually ourselves, may have originated in distant galaxies. How exciting is that?

“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,” Daniel Anglés-Alcázar, a postdoctoral fellow in Northwestern’s astrophysics center and the lead researcher on the study, said in a press release.

A team of astrophysicists at Northwestern University ran supercomputer simulations which demonstrated a curious phenomenon called intergalactic transfer. It turns out that supernova explosions cause the ejections of huge amounts of gas from their galaxies, which leads to the fact that atoms travel across space, carried by intergalactic winds.

Such an intergalactic voyage of an atom is estimated to take billions of years due to enormous distances between galaxies, even though the galactic winds are extremely powerful, with the speed of several hundred kilometers per second.

With the help of the FIRE (“Feedback In Realistic Environments”) simulation system, the research team created 3D models of galaxies as they have been since right after the Big Bang to this day. The astrophysicists then tracked the flows of matter in these simulated galaxies. Thanks to sophisticated algorithms, the acquired data were analyzed to find out how galaxies evolved and where their matter came from.

As a result, it was found that gas tends to flow from smaller galaxies to larger ones, such as our Milky Way. It has to do with the fact that larger galaxies have a greater gravitational pull, which makes it difficult for atoms to escape them.

According to the estimates based on the simulations, approximately half the matter in the Milky Way could have been originated elsewhere. The researchers say atoms in our galaxy could have come from one million light years away! Thus, we are indeed made of stardust, and it had to travel billions of years of time and millions of light years of distance to find its new home in our galaxy.

Professor Claude-André Faucher-Giguère, who participated in the study, said:

“Our origins are much less local than we previously thought. This study gives us a sense of how things around us are connected to distant objects in the sky.”