We are made of a chemical element that originated outside the Milky Way: what we know.

Life on Earth would not exist without carbon. However, carbon and other chemical elements heavier than helium and hydrogen are formed after the death of massive stars, which explode in supernovae. From these elements, new stars and planets eventually emerge. Carbon, created billions of years ago, became a crucial component of Earth and later an integral part of the human body. Astronomers have discovered that carbon and other heavy chemical elements do not merely drift around our Milky Way galaxy in the circumgalactic medium, but return to the galaxy to participate in the creation of new objects. This research has been published in The Astrophysical Journal Letters, reports Interesting Engineering.

Gas Cloud Surrounding the Galaxy

As early as the 1950s, astronomers found the first evidence of the circumgalactic medium, a vast gas cloud surrounding the Milky Way and other galaxies. The circumgalactic medium can extend hundreds of thousands of light-years from the galaxy.

In 2011, using the Hubble Space Telescope, scientists found the first confirmation of a long-standing theory. It was suggested that this medium could act as a conveyor, redirecting expelled heavy chemical elements back into the galaxy to facilitate the formation of new stars and planets.

The new research supports this hypothesis and shows that there is a vast amount of carbon in the circumgalactic medium that is constantly moving back into galaxies. Additionally, scientists discovered that there is not only a significant amount of carbon but also oxygen present in the circumgalactic medium.

Human Bodies Are Composed of Carbon That Came from Beyond the Milky Way

Scientists believe that after supernova explosions, many heavy chemical elements are ejected beyond galaxies, but then they return and, under the influence of gravity, become components of new stars and planets. Billions of years ago, this allowed carbon to become part of our planet and later one of the key elements in the human body.

Light from various sources passes through the circumgalactic medium, and different chemical elements absorb this light. Astronomers have used this information to determine the chemical composition of the circumgalactic medium.

Using the Hubble Telescope, astronomers studied the interaction of quasar light with the circumgalactic medium of their host galaxies, where new stars are born. Quasars are the brightest objects in a galaxy, created by actively feeding supermassive black holes that consume vast amounts of matter.

Some of the light from quasars was absorbed by large amounts of carbon, as well as oxygen associated with other elements. The study revealed that carbon spreads up to 400,000 light-years from its host galaxy, which is four times the diameter of the Milky Way. Scientists believe that the carbon currently within our bodies was once part of the circumgalactic medium beyond the Milky Way.

The authors of the study aim to identify what other heavy chemical elements are circulating around galaxies to eventually return to their cores. Scientists believe that a complete understanding of what creates the circumgalactic medium could provide valuable insights into how galaxies form and what events they may experience in the future.