There’s been a problem with the universe. Some matter has been missing — the ordinary type that makes up atoms. The good news: Astronomers say they may have found it.
Scientists think this missing matter is hot gas. It appears to be lurking in spaces between clusters of galaxies.
Previous studies had hinted where this missing matter might be hiding. A new search technique now is helping home in on where it resides. Astronomers described online the technique they used in a pair of papers posted September 15 and 29 at arXiv.org.Finding this missing matter is important, says Dominique Eckert. He is an astronomer at the Max Planck Institute for Extraterrestrial Physics in Garching, Germany. He did not take part in the new work. He has, however, searched for the missing matter. It is made of protons, neutrons and other select subatomic particles. Scientists sometimes refer to these as baryons (BEAR-ee-ahns). “If you want to understand how galaxies form and how everything forms within a galaxy, you have to understand the evolution of the baryon content,” says Eckert. And that starts with knowing where those baryons are.
Astronomers know that about 85 percent of the matter in the universe is dark matter. This stuff is mysterious and elusive. And it’s not made of baryons. It doesn’t emit light (which is why it’s literally dark). It’s also different from ordinary matter.
In contrast, ordinary matter makes up only about 15 percent of the mass of the universe. It is what is in us and all around us. Weirdly, about half of even this type of matter does not show up astronomers scan the skies. As they look at galaxies within the nearest few billion light-years from Earth, they find only about half the baryons that should have been produced in the Big Bang. (That’s the rapid expansion of dense matter in the universe. According to current theory, the Big Bang marked the origin of the universe. )
The rest of the ordinary matter is probably hiding in long strands, or filaments, of gas. These strands connect clusters of galaxies…
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