Intergalactic carbon in our bodies

The carbon in our bodies not only comes from interstellar space but, according to a new study, probably traveled through intergalactic space.

Life on Earth could not exist without carbon. But carbon itself could not exist without stars. Almost all chemical elements, except hydrogen and helium, owe their current presence in the universe to the fact that they were forged into stars and subsequently thrown into the cosmos when they died. In a supreme act of galactic recycling, planets like ours are formed by incorporating these stellar atoms into their composition, whether it be the iron in the Earth’s core, the oxygen in its atmosphere, or the carbon in the bodies of Earthlings.

A team of scientists from the United States and Canada has recently confirmed that carbon and other chemical elements formed in stars do not always remain within the galaxy in which they were created. In galaxies like ours, which continue to actively form new stars, enormous quantities of atoms of these chemical elements make a tortuous journey that includes intergalactic space. They leave their home galaxy and circulate around it in giant streams that extend through intergalactic space. These currents, in what is known as the circumgalactic medium, resemble giant conveyor belts that push material outward and drag it back into the galactic interior, where gravity and other forces can use these raw materials to form planets, moons, , asteroids, comets and even new stars.

“The circumgalactic environment is like a gigantic train station: It constantly sends cargo in and out,” explains Samantha Garza, from the University of Washington in the American city of Seattle, and co-author of the study. Heavy chemical elements made in stars are pushed out of their host galaxy and into the circumgalactic environment by the supernova-type explosions in which such stars die. But then, out there, they can be drawn back in, re-enter the galaxy, and continue the cycle of star and planet formation.

Sector of intergalactic space with the galaxy JO175 in the center. (Photo: ESA / Hubble / NASA / M. Gullieuszik / GASP team)

In 2011, a team of scientists confirmed for the first time the theory that galaxies with significant star-forming activity like ours are surrounded by a circumgalactic medium, and that this large cloud of circulating material includes hot, oxygen-enriched gases. Garza and his colleagues have now discovered that the circumgalactic medium of galaxies with significant star formation activity also circulates materials at lower temperatures, including carbon.

The implications of this phenomenon are exciting, in the words of Jessica Werk, from the aforementioned university and co-author of the study. “It is very likely that the carbon in our own bodies has spent a significant amount of time outside the galaxy!”

The study is titled “The CIViL* Survey: The Discovery of a C iv Dichotomy in the Circumgalactic Medium of L* Galaxies.” And it has been published in the academic journal The Astrophysical Journal Letters. (Fountain: NCYT by Amazings)