Let this sink in your chest: the oxygen in every breath you take was formed within the stars. But new research from NASA’s Hubble Space Telescope shows that small galaxies expel most of the oxygen their stars produce. Astronomers studied 37 nearby dwarf galaxies, containing anywhere from a few thousand to hundreds of millions of stars. On average, those galaxies retained only 11 percent of the oxygen their stars produced over time. The most efficient kept about a quarter; the worst among them kept only 4 percent. Much larger galaxies tend to have three to four times as many, previous studies have shown. The exploding stars probably scared away the rest. When massive stars die in explosions called supernovae, they unleash winds strong enough to blow gas out of a galaxy. Dwarf galaxies have weak gravity, so they struggle to hold on to that material. Astronomers want to know where the oxygen produced by stars ends up and how much a galaxy can store. A project called Galaxies Losing Oxygen through Winds, or GLOW, tracks that oxygen inside the stars, through the gas between them, and into the space between the galaxies. Because oxygen outnumbers all elements except hydrogen and helium, it is a good indicator of how galaxies generally recycle matter. Astronomers can easily measure it and know how stars produce it. “So we actually chose oxygen for practical reasons,” Kristen Wingfield McQuinn, GLOW principal investigator at the Baltimore Space Telescope Science Institute, said in a statement. SEE ALSO: Oh wow. Martian volcanoes may still be alive. To count oxygen, the team used Hubble images sharp enough to distinguish individual stars. Few dwarf galaxies are close enough to allow that kind of detail. Mashable Light Speed Those images revealed each galaxy’s star birth history and, from there, how much oxygen it should have produced. The study appears in The Astrophysical Journal. The research team then measured what was left. Almost all the oxygen was in the gas of each galaxy, not in its stars. Data from radio and infrared telescopes completed the rest of the picture. Location also seems to matter. Galaxies in populated areas and within about 3 million light years of a large galaxy tended to retain more oxygen. Those furthest from a large neighbor were left with less than 15 percent. Surrounding gas can push lost oxygen into a galaxy, according to the paper, or the galaxy can pick up oxygen that its neighbors expelled. The researchers caution that the pattern is based on only a handful of galaxies. But the final fate of the oxygen remains unknown. Previous studies found only a trace of the oxygen these galaxies produced (between 1 and 7 percent) in the thin halo of hot gas that surrounds a galaxy. Even counting the colder gas, those halos probably contain at most about a third of the oxygen that the galaxies’ stars produced. Much of the rest probably escaped into intergalactic space, but scientists can’t say for sure. McQuinn, who also directs science operations at the Nancy Grace Roman Space Telescope, plans to use the new observatory to find even smaller, fainter galaxies. It then plans to study its stars with Hubble and the James Webb Space Telescope. Grace Telford, an astronomer at the University of Utah who is part of the team, is using Hubble to get close to massive stars that produce oxygen and expel it. If most of the missing oxygen were to escape, the smallest galaxies in the universe could be the biggest oxygen spreaders, seeding space with the same element that fills your lungs. Do you want to receive more science and technology news directly to your inbox? Sign up for Mashable’s Top Stories newsletter today.
