According to a recent study by U.S. and Canadian scientists, the carbon in our bodies may have traveled far beyond our galaxy before becoming part of Earth. Published in the Astrophysical Journal Letters, the research confirms that carbon and other elements forged in stars do not remain stationary in space but circulate through a vast cosmic conveyor belt -- the circumgalactic medium (CGM) -- surrounding star-forming galaxies like the Milky Way.
The CGM is a massive reservoir, expelling and drawing in star-forged materials like carbon and oxygen. "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 doctoral candidate at the University of Washington, in this article on the university's website."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."
This recycling process is essential to galaxy evolution, says co-author Jessica Werk, a professor at the University of Washington. "The same carbon in our bodies most likely spent a significant amount of time outside the galaxy!"
Using the Hubble Space Telescope's Cosmic Origins Spectrograph, the team analyzed light from nine distant quasars passing through the CGM of 11 star-forming galaxies. The data revealed substantial amounts of carbon extending nearly 400,000 light-years into intergalactic space -- about four times the diameter of the Milky Way.
In 2011, researchers confirmed the existence of the CGM and its oxygen-enriched gases. This latest study builds on those findings, demonstrating that more remarkable materials like carbon circulate in the CGM and are vital to the star and planet formation cycle.
Understanding the CGM's recycling role is crucial for learning why star formation eventually slows down in galaxies. "If you can maintain the cycle -- pushing material out and pulling it back in -- then theoretically, you have enough fuel to keep star formation active," Garza notes. A breakdown of this process could explain why galaxies transition into periods of low star formation over time.
The team plans to investigate other elements in the CGM and compare their roles in galaxies with active star formation versus those with declining activity. Such research could illuminate the processes transforming galaxies from vibrant star-forming regions into "stellar deserts."
Researchers from institutions across North America, including the Herzberg Astronomy and Astrophysics Research Centre, the University of Colorado Boulder, and North Carolina State University, co-authored the study, which was funded by NASA and the National Science Foundation.
This work highlights the interconnectedness of cosmic and terrestrial processes, emphasizing the journey of carbon and other elements from distant galaxies to the building blocks of life on Earth.