Stars manufacture oxygen, but the galaxies containing them do not necessarily keep it. A study of 37 nearby dwarf galaxies found that they retained between 4% and 25% of the oxygen their stars were estimated to have produced, with an average of about 11%.
The result turns the familiar image of a galaxy as an island of stars into something more active: a system exchanging material with its surroundings. NASA highlighted the work on November 2, 2026, following publication in The Astrophysical Journal. The GLOW II research preprint had first appeared on August 7 and was revised on August 13.
An oxygen budget built from several telescopes
The researchers compared the oxygen expected from the galaxies’ histories of star formation with the amount remaining in their stars, gas and dust. Nearly all the retained oxygen was in the gas, according to the paper. The average is a result for this selected sample of low-mass, gas-rich systems, rather than a universal percentage for every small galaxy.
The companion GLOW I data atlas explains the observational groundwork. It combines Hubble images resolving individual stars with Spitzer infrared observations, radio measurements of atomic hydrogen from the Very Large Array and ground-based optical data.
Those observations do different jobs. Individual stars help reconstruct how a galaxy assembled its stellar population. Gas measurements describe another reservoir of material. Measurements of chemical abundance connect that reservoir with the elements the stars have produced.
The resulting budget resembles an account reconstructed from several kinds of record. No single photograph contains a direct label giving the oxygen manufactured over the galaxy’s lifetime. The total requires observations and models of stellar populations, followed by comparison with the material detected now.
This explains the importance of selecting nearby galaxies. Hubble can distinguish individual stars in these systems, providing information that would be blended together in a more distant object. The sample trades breadth across the universe for a more detailed view of the chosen galaxies.
The missing material may be outside the visible galaxy
In its November 2 explanation, NASA links the oxygen shortfall to the effects of massive stars and supernova explosions. Their energy can drive material outward in galactic winds. Low-mass galaxies appear to lose oxygen more effectively than the simulations discussed in the study predict.
The destination remains an open question. Some oxygen could be in the diffuse gas surrounding a galaxy, called the circumgalactic medium. Some may have travelled farther into the space between galaxies. Finding a shortfall in the central system does not by itself map the missing material’s full route.
That distinction creates a productive research problem. A model needs to explain how much oxygen the stars make, how much remains and how the rest moves through surrounding space. Matching one observed relationship does not guarantee that it represents the whole cycle accurately.
Material can also return. A galaxy’s present composition reflects production, loss, inflow and recycling over time. The research therefore tests a history of exchange rather than a single explosive event.
A familiar element becomes a tracer of galaxy evolution
The Rutgers research-team account explains why oxygen is useful: it is abundant, detectable and its production in stars is relatively well understood. Light at characteristic wavelengths helps astronomers identify it and estimate its abundance.
The oxygen discussed here includes atoms and ions in stars and interstellar material. It should not be imagined as a disappearing reservoir of breathable air. In astronomy, tracking this element helps follow the broader movement of material made by stars.
The visual contrast between Hubble and Webb images of NGC 4449 illustrates another principle: different wavelengths reveal different aspects of the same object. A vivid new image can complement an investigation without replacing the quantitative measurements needed for a chemical budget.
The team’s proposed follow-up includes closer study of individual massive stars and searches for still fainter nearby galaxies. Those observations would examine the producers and possible exporters of oxygen alongside systems where the balance may differ. The larger scientific question is how small galaxies enrich their surroundings, helping distribute the ingredients from which later generations of stars and planets can form.
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