In a major breakthrough for cosmology scientists have located the long-missing half of the Universe’s visible matter revealing it has been hiding in enormous clouds of ionized hydrogen drifting in intergalactic space. These faint previously undetectable gas clouds form a vast mist surrounding galaxies far beyond where astronomers had looked before.
An international team led by Boryana Hadzhiyska, a Miller Postdoctoral Fellow at UC Berkeley used a novel technique to detect the elusive matter. The results, which involve contributions from 75 scientists worldwide have been submitted to Physical Review Letters and are available as a preprint on arXiv.
Hadzhiyska says “For years half of the Universe’s baryonic matter the normal matter that makes up stars, planets, and people was unaccounted for, Now it appears that this missing mass exists as hot ionized hydrogen gas spread across cosmic space.”
Using data from galaxy surveys and sophisticated models, the team detected subtle signals from diffuse hydrogen gas halos extending far beyond galactic boundaries. These halos are too faint to be seen directly, but their presence can be inferred through light distortions and temperature imprints on the cosmic microwave background radiation.
Her collaborator Simone Ferraro, senior scientist at Lawrence Berkeley National Laboratory, said the findings match predictions from earlier hints of ionized hydrogen halos seen in past analyses. “The measurements are consistent with the idea that we’re finally seeing all the gas that was expected,” Ferraro noted.
For years models of the Universe structure indicated that only about half of its baryonic matter was accounted for through observations. This missing matter mystery puzzled astronomers, especially since dark matter and dark energy which make up most of the Universe were already known to be invisible and untraceable through direct observation.
Now, this discovery strengthens the theory that this baryonic matter wasn’t lost it was simply spread out in thin hot intergalactic filaments, impossible to detect with traditional instruments. These hydrogen mists were likely expelled by galactic winds and energetic processes near supermassive black holes.
The researchers are now running more detailed simulations to better quantify the amount and distribution of this hidden matter. If confirmed, this discovery completes the picture of the Universe’s visible matter and marks a major step forward in understanding the large-scale structure of the cosmos.
