Atoms forged into stars follow a giant, winding path before being incorporated into future generations of stars and planets, new research reveals. This route is so indirect that it takes these atoms outside the conventional definition of the galaxy. In other words, some of the remnants of long-gone stars left the galaxy before being drawn back to form the Earth and eventually ourselves. This is where the atoms in your body have traveled!
All elements except hydrogen and helium form in stars, most often during dramatic events such as supernovae. Astronomers originally believed that supernovae and possibly more exotic events in our galactic region created most of the atoms that make up Earth and other rocky planets. However, researchers gradually discovered that massive currents in the Milky Way and other similar galaxies, known as the circumgalactic medium, mix these products for billions of years before conditions become favorable for star and planet formation.
“Think of the circumgalactic medium as a giant train station: it’s constantly pushing material out and bringing it back in,” explained Samantha Garza, lead author of the study and a PhD student at the University of Washington (USA).
The atoms in your body have spent a long time outside the galaxy
“Heavy elements produced by stars are ejected from the host galaxy and into the circumgalactic medium through the explosive death of supernovae, from where they can later be drawn back and reintegrated into the cycle of star and planet formation,” she says, cited by IFL Science.
“The implications for galaxy evolution and the nature of the carbon pool available for new star formation are fascinating. It is very likely that the atoms in your body have spent a significant amount of time outside the galaxy!” adds Professor Jessica Werk, co-author of the study.
Understanding of this subject is just beginning, with the existence of the circumgalactic medium being confirmed in 2011. While hydrogen is the main component, the oxygen originally identified there had to come from within the galaxy. Garza, Werk and their colleagues have now identified the presence of carbon, demonstrating that it follows a similar route.
Essentials for life
Another recently discovered phenomenon, Odd Radio Circles (ORCs), could be made up of material ejected from galaxies by multiple supernova explosions. However, these materials are permanently lost, unlike the slower process in the circumgalactic medium, which allows atoms to be recycled.
“If you keep the cycle going, pushing material out and pulling it back in, you theoretically have enough fuel to support star formation,” Garza explained. The authors suspect that a disruption in this process could explain why some galaxies prematurely stop forming stars.
To detect elements in the circumgalactic medium, the team collected the light of nine quasars that traversed the circumgalactic medium from 11 active star-forming galaxies before being intercepted by the Hubble Space Telescope. The observations were compared to passive galaxies, where star formation has stopped.
The Cosmic Origins spectrograph revealed the abundant presence of carbon around active galaxies, in some cases at distances of up to 400,000 light-years, four times the length of the Milky Way. In contrast, the detection of carbon around passive galaxies was three times rarer.
The team hopes that future observations will confirm their hypothesis that perturbations from carbon recycling contribute to the loss of activity in passive galaxies.
Although the presence of other heavy elements in this environment remains to be confirmed, magnesium has already been found to be more widespread around active galaxies.
Finally, although we need a variety of elements to form a human, carbon and oxygen are two of the five essential for known life. Thus, we are not just “stardust”, but stardust that has traveled a long way.
The study is published in The Astrophysical Journal Letters.
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Source: www.descopera.ro
