The carbon in our bodies has been outside our galaxy, but then returned

A study by scientists from the University of Washington suggests that the atoms in our bodies have traveled not only to interstellar space, but also to intergalactic space. For the first time, spectral measurements have shown that in the halos of galaxies there are huge reservoirs of carbon, which enters the galaxies and leaves them, thus circulating for billions of years and participating in the evolution of galactic objects.

Image source: NASA

Elements heavier than hydrogen and helium—including carbon, oxygen and iron—are thought to be born in stars and spread throughout galaxies and beyond after supernova explosions. New research indicates that such elements can remain in the halos of galaxies for a long time, repeatedly returning to the galactic disks and participating in the processes of star formation, the formation of planets and other objects, including you and us and biological organisms in general.

In 2011, it was proven that galaxies with ongoing star formation are surrounded by oxygen reserves. The halo of matter extends over a distance of up to 400 thousand light years, which is three to four times the size of the galaxies themselves. New research shows that in addition to oxygen, these reservoirs also contain huge amounts of carbon, an element of particular interest in terms of the possibility of biological life.

Scientists used light from nine distant quasars to analyze the environment around 11 galaxies that are still forming stars. Data on the absorption of light waves by the medium were obtained using the Cosmic Origins spectrograph on the Hubble Space Telescope. The circumgalactic environment turned out to be saturated with carbon. Researchers believe this is key to understanding the evolution of galaxies, in particular why they retain the ability to form stars for so long. The matter ejected from stars during supernova explosions does not immediately escape into the Universe, but remains for a long time in the halos of galaxies and returns to the galactic disks, where it participates in the formation of new stars and planets.

«Think of the circumgalactic environment as a giant train station: it is constantly pushing material out and pulling it back in, the scientists explain. — The heavy elements that make up stars are ejected from their host galaxy into the circumgalactic environment as a result of supernova explosions. These elements can then be pulled back in, continuing the cycle of star and planet formation.”

Studying the dynamics of the circulation of matter in circumgalactic environments is important for understanding how and at what speed galaxies turn into deserts, where star formation stops. This also allows us to better understand the duration of the stages of galaxy evolution.

«For the evolution of galaxies and nature in general, the presence of a reservoir of carbon available for the formation of new stars is an exciting discovery, the study authors write. “The same carbon that makes up our bodies has likely spent significant time outside the galaxy!”