Small dwarf galaxies retain just 11 percent of the oxygen their stars produce, according to a study published on November 2, 2026, in The Astrophysical Journal.
Astronomers examined 37 nearby dwarf galaxies holding anywhere from a few thousand to hundreds of millions of stars. They used data from the NASA/ESA Hubble Space Telescope.
Simulations predicted that significantly more of the element should remain. Researchers discovered that the most efficient dwarf galaxies kept about a quarter of their forged oxygen. The lowest-retention systems held onto just 4 percent.
The team looked at dwarf galaxies within roughly 19.5 million light-years of Earth. These systems feature stellar masses from about 3 million to 3 billion times that of the Sun. Nearly all of the oxygen that did stay behind resides in gas rather than in dust or stars.
The research forms part of the Galaxies Losing Oxygen via Winds (GLOW). NASA and the National Science Foundation funded the project.
The team used archival optical imaging from Hubble to resolve individual stars. They determined star formation histories and how much oxygen should have been generated over time.
They combined these observations with data from NASA’s retired Spitzer Space Telescope alongside the ground-based Very Large Array and Australia Telescope Compact Array.
Oxygen outnumbers every element except hydrogen and helium and gives off easily detectable light. Scientists use it as a reliable tracer for how galaxies recycle and distribute matter.
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,
Kristen Wingfield McQuinn, GLOW principal investigator
Kristen Wingfield McQuinn serves as GLOW principal investigator. She also serves as mission head of the Science Operations Center for NASA’s newly launched Nancy Grace Roman Space Telescope at the Space Telescope Science Institute in Baltimore.
Where's the oxygen? After researchers studied nearby dwarf galaxies, they realized much of the oxygen they expected to see was missing. Galactic winds from supernova explosions are apparently more effective at removing oxygen than current models predict: https://t.co/h9Wns2NvY6 pic.twitter.com/Q5fjsH0lBE
When massive stars die in supernova explosions, they unleash powerful winds. These winds drive material out of host galaxies and into the space between them.
Dwarf galaxies feature relatively weak gravity. They struggle to retain that gas. Grace Telford, an astronomer at the University of Utah and co-author of the study, explained the mechanics of the loss.
We know that the oxygen had to be inside of the galaxies at some point in the past, so the oxygen must have been ejected. And to do that, you need energy from massive stars and supernova explosions to drive material out of the host galaxies and into the space between galaxies,
Grace Telford, an astronomer at the University of Utah
Telford is continuing her work by using Hubble to zoom in on individual, massive stars that produce oxygen and eject it from their host galaxies.
Astronomers have previously detected oxygen in the gas halos surrounding dwarf galaxies. Researchers have detected oxygen in those halos.
It remains unclear whether most of that missing material stays trapped within those surrounding regions. It remains unclear if it has traveled farther out into the intergalactic medium, leaving 37 observed systems with masses between 3 million and 3 billion solar masses.
