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All carbon in the universe forms in the fiery cores of stars, but the element that makes up 18% of our bodies may have taken a detour through the outer edges of our galaxy—and perhaps even into intergalactic space—on veritable “cosmic conveyor belts” before reaching Earth, according to new research.
Astronomers in the U.S. and Canada have revealed that the circumgalactic medium—a vast, complex halo of gas surrounding galaxies—stores carbon (among other materials) far from the galaxy before recycling it back into the star-forming regions where it originated, contributing to the formation of planets, moons, new stars, and other celestial bodies. The discovery, detailed in a December 27 study published in The Astrophysical Journal Letters, could have important implications for our understanding of galactic evolution.
Scientists confirmed the existence of the circumgalactic medium in 2011, describing it as a vast, circulating cloud around star-forming galaxies like the Milky Way that contributes to recycling hot, oxygen-rich gases. Now, researchers from the new study demonstrate that lower-temperature material, including carbon, can also hitch a ride on this “cosmic conveyor belt,” as it’s described in a press release.
“We can now confirm that the circumgalactic medium acts like a giant reservoir for both carbon and oxygen,” Samantha Garza, an astronomer from the University of Washington who participated in the study, said in the university statement. “And, at least in star-forming galaxies, we suggest that this material then falls back onto the galaxy to continue the recycling process.”
This recycling of stellar material is crucial for the formation of new celestial bodies, while the recycling of carbon—often called the building block of life—is essential for the formation of our bodies and all living things.
“Think of the circumgalactic medium as a giant train station: It is constantly pushing material out and pulling it back in,” Garza explained. “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.”
Garza and her colleagues used the Cosmic Origins Spectrograph on the Hubble Space Telescope to detect how the circumgalactic medium of 11 star-forming galaxies impacts nine distant quasars (extremely bright galactic cores). Their analysis revealed that some of the quasars’ light is absorbed by an abundance of carbon in the circumgalactic medium—carbon that in some cases was channeled out nearly 400,000 light years beyond its original galaxy. That’s four times the diameter of the Milky Way.
“The implications for galaxy evolution, and for the nature of the reservoir of carbon available to galaxies for forming new stars, are exciting,” said Jessica Werk, a co-author on the study also from the University of Washington. “The same carbon in our bodies most likely spent a significant amount of time outside of the galaxy!”
Further research could provide more insight into how the materials channeled by the circumgalactic medium impacts the number of stars formed in a galaxy. One theory, for example, hypothesizes that the eventual decrease or end of the circumgalactic medium’s involvement in the cosmic recycling process could contribute to a galaxy’s declining population of stars.
“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,” said Garza.
So even though you may wish you had more time to travel, rest assured that at least your carbon atoms had quite the intergalactic voyage before ending up in your body.
