Intergalactic gas is a diffuse plasma that permeates the entire universe. It consists of about 96% hydrogen and 4% helium by mass, with trace amounts of other elements such as carbon, oxygen, and nitrogen. The vast majority of intergalactic gas is in the form of atomic hydrogen (H I), which emits a characteristic 21-cm radio wavelength line when it is excited by ultraviolet radiation from stars.
Intergalactic gas plays an important role in the formation and evolution of galaxies. It serves as the fuel for star formation, providing the material out of which new stars are born. Additionally, intergalactic gas provides a means for matter to be recycled between galaxies through processes such as galactic winds and supernovae. By understanding how this gas behaves, astronomers can better understand how galaxies evolve over time.
The study of intergalactic gas has been revolutionized in recent years by advances in technology. Large radio telescopes have been used to map out H I distribution across the sky, while sensitive X-ray detectors have allowed astronomers to detect even more diffuse plasma between galaxies. These observations have led to a greater understanding of how intergalactic gas behaves on both large and small scales.
Intergalactic gas is an important part of the universe and its study can provide insights into some of its most fundamental processes.