The carbon atoms in your body likely took an incredible journey before becoming part of you—traveling hundreds of thousands of light-years into space and back on a vast cosmic “conveyor belt,” according to new research.
Scientists have discovered that the atoms making up living things don’t just drift randomly through space after being created in dying stars. Instead, they travel on enormous currents extending far beyond their galaxies of origin, eventually being recycled into new stars, planets, and even life forms.
A Cosmic Recycling System
“Think of the circumgalactic medium as a giant train station: It is constantly pushing material out and pulling it back in,” explains Samantha Garza, lead author and University of Washington doctoral candidate. “The heavy elements that stars make get pushed out of their host galaxy and into the circumgalactic medium through their explosive supernovae deaths, where they can eventually get pulled back in and continue the cycle of star and planet formation.”
Your Atoms’ Epic Journey
“The implications for galaxy evolution, and for the nature of the reservoir of carbon available to galaxies for forming new stars, are exciting,” says co-author Jessica Werk, professor and chair of the Department of Astronomy at the University of Washington. “The same carbon in our bodies most likely spent a significant amount of time outside of the galaxy!”
Mapping the Invisible
Using the Hubble Space Telescope’s Cosmic Origins Spectrograph, researchers measured light from nine distant quasars passing through the circumgalactic medium of eleven star-forming galaxies. The measurements revealed vast amounts of carbon, in some cases extending nearly 400,000 light-years into intergalactic space—four times the diameter of our own galaxy.
A Vital Process for Galaxy Life
The research suggests that this recycling process is crucial for maintaining a galaxy’s ability to form new stars. When the process slows or breaks down, it may explain why some galaxies stop producing stars over long periods.
“If you can keep the cycle going — pushing material out and pulling it back in — then theoretically you have enough fuel to keep star formation going,” notes Garza.
Looking to the Future
The researchers are now working to determine the full extent of other elements circulating in this cosmic recycling system and to understand how the process differs between galaxies that are actively forming stars and those that have largely ceased star formation. These answers could help explain not just when galaxies like ours transition into stellar deserts, but why.
The research was published in The Astrophysical Journal Letters on December 27, 2024. The study was funded by NASA and the National Science Foundation.
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