University of Washington researchers have uncovered a cyclical process in which carbon atoms, formed in stars, leave their galaxy, travel through intergalactic space, and finally return to participate in the formation of new stars and planets..
Carbon, the essential element for life on Earth, is a product of exploding stars and creates an incredible cosmic cycle of materials in the universe.
Almost all the elements, except hydrogen and helium, are created in the furnaces of stars and are dispersed into space during their turbulent deaths. In the action of a global galactic cycle, planets like Earth were formed from the combination of these atoms, including iron in the Earth's core, oxygen in the atmosphere, and carbon in our bodies.
A team of scientists from the United States and Canada revealed that the atoms formed in stars do not move through space randomly. In active galaxies, where new stars are still being formed, these atoms undergo complex trajectories. They move in huge "currents" that extend into intergalactic space, called halos or intergalactic medium (Halo, Circumgalactic Medium). This system functions like a "cosmic conveyor belt" - pushing materials out, bringing them back in and filling the galaxy with the ingredients needed to create new stars and planets.
A periodic system for the formation of stars and planets
According to Samantha Garza, a doctoral student at the University of Washington and lead author of the study: "Think of the circumgalactic medium as a giant train station. It pushes material out and brings it back in. The heavy elements that form in stars are pushed into this medium by supernovae, and then pumped back in to form new stars and planets ."
The study, published on December 27 in the journal Astrophysical Journal Letters, provides evidence that this system serves as a central reservoir of materials such as carbon and oxygen in active galaxies.
In 2011, scientists first confirmed the theory that active galaxies are surrounded by halos made up of hot gases rich in oxygen. The current research confirms that the medium also includes cooler material, such as carbon.
According to Garza, "We can now confirm that the halo acts as a huge reservoir for carbon and oxygen, and in active galaxies these materials are drawn back to continue the recycling process."
Why do galaxies stop producing stars over time?
The researchers used the device Cosmic Origins Spectrograph on the Hubble Space Telescope to measure the effect of the halo on the light of nine distant quasars - exceptionally bright light sources in the universe. The measurements revealed that the quasars' light was absorbed by carbon in the halo as the carbon cloud extended to about 400,000 light-years, four times the diameter of our galaxy.
According to the researchers, understanding the role of the halo in the circulation of materials in galaxies can shed light on the reasons why some galaxies stop forming stars over time.
"If the cycle continues - pushing the materials out and putting them back in - then theoretically there is enough 'fuel' to continue forming stars," Garza said.
Future research will attempt to quantify the halo components in different galaxies and examine the differences between active galaxies and galaxies that have stopped producing stars. These discoveries may shed light not only on when galaxies transition to a "stellar desert" state, but also on the reasons for this.
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