In an unexpected discovery, astronomers using NASA’s Hubble Space Telescope say that something appears to be missing from more than three dozen nearby dwarf galaxies.
The cosmic cold case involves oxygen that researchers expected to be produced by the stars in these galaxies, which, according to new research published in The Astrophysical Journal, now suggests strong stellar winds produced by these stars and supernova explosions could effectively be stripping that oxygen away, and far more efficiently than current models anticipated.
The research, undertaken through the Galaxies Losing Oxygen via Winds (GLOW) project, combined observations made using Hubble with existing data obtained using NASA’s now retired Spitzer Space Telescope, as well as recent data obtained from ground-based radio telescopes.
The data was used to assist astronomers in reconstructing the star formation in these dwarf galaxies over the course of their histories, allowing them to estimate how much oxygen their stars should have produced, and compare those predictions with the amounts currently detectable.
“Oxygen is produced by stars, which are inside of galaxies,” explained University of Utah astrophysicist O. Grace Telford, one of the recent study’s co-authors.
“We know that the oxygen had to be inside of the galaxies at some point in the past,” Telford said, “so the oxygen must have been ejected.”
While astronomers do suspect that much of the currently “missing” oxygen was expelled into the surrounding space, its exact whereabouts have not been determined based on current data.
Still, the findings point to the fact that dwarf galaxies appear to retain only a small fraction of the oxygen generated by their stars. This could mean that scientists may be forced to revise existing models about how galaxies distribute heavy elements throughout the universe.
In the future, additional observations made by Hubble, as well as its successors, the James Webb Space Telescope and the Nancy Grace Roman Space Telescope, could provide additional information that may help astronomers determine once and for all where the “missing” oxygen is going.
“Oxygen is one of the primary elements formed by stars. Being able to trace how much oxygen gets made, and then how much is distributed inside and outside of galaxies, helps us understand galaxy evolution,” said Kristen W. McQuinn, one of the study’s co-authors who also serves as the GLOW principal investigator, and mission head of the Science Operations Center for NASA’s new panoramic Nancy Grace Roman Space Telescope at the Space Telescope Science Institute in Baltimore, Maryland.
“It also helps us learn where and how much galaxies are enriching the space between galaxies, called the intergalactic medium,” McQuinn added.
The recent study, “GLOW. II. A Census of Oxygen in Low-mass Galaxies,” was published in The Astrophysical Journal.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. A longtime reporter on science, defense, and technology with a focus on space and astronomy, he can be reached at micah@thedebrief.org. Follow him on X @MicahHanks, and at micahhanks.com.