Nearly half of the universe’s ordinary matter was uncharted, until now
Nearly half of the universe’s ordinary matter has been hiding — until now.
Bursts of radio waves have illuminated the whereabouts of all ordinary matter, revealing its distribution between, around and within galaxies, researchers report June 16 in Nature Astronomy. And X-rays have uncovered details about a once hidden string of gas linking four galaxy clusters, another team reports in the June Astronomy and Astrophysics.
“The two papers are very complementary,” says astrophysicist Jason Hessels of McGill University in Montreal, who was not involved in either study. While one takes a statistical approach to fill in the matter gap, the other measures a specific slice of it.
Ordinary matter makes up everything that can be observed, such as planets and people. It’s made of standard particles like protons and neutrons, collectively called baryons. But it accounts for just about 15 percent of all matter in the universe. The rest is the mysterious dark matter.
Almost half of ordinary matter is scattered like fine mist, so it’s hard to detect. “This gas is missing in the sense that theoretical models expect that it should be … in certain places,” Hessels says. “But how much of it is where and actually showing that that is true is very difficult because the gas is very, very diffuse.” [Continue reading…]