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Hubble study finds small galaxies retain little of their stars’ oxygen

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First brief 3 Nov, 9:35 pm IST Updated 3 Nov, 9:35 pm IST 0 developments 3 min read

NGC 4449. — NASA, ESA, Hubble Heritage–ESA/Hubble Collaboration, Alessandra Aloisi (STScI, ESA) · NASA reuse

Where it stands

A study of 37 nearby dwarf galaxies has found that they retain little of the oxygen their stars produced. These small galaxies kept between 4% and 25%, with an average of about 11%. The research was published in The Astrophysical Journal and presented by NASA on 2 November 2026. Stars make oxygen and release it into surrounding gas during their lives and deaths. Scientists compared the amount the stars were expected to produce with the amount remaining in each galaxy. The large gap points to powerful flows of gas carrying much of that oxygen away. The result matters because a galaxy’s development depends on both making new elements and retaining the material needed for later stars. Current computer models predict that these small galaxies should keep more oxygen than the observations suggest. The findings give researchers a way to test how those models handle gas escaping from galaxies. The destination of most of the missing oxygen remains an open question. Some may be in the thin gas surrounding the galaxies, while some may have travelled farther into the space between them.

Background

A galaxy is a large system of stars, gas and dust held together by gravity. Stars form from gas within it. Inside stars, nuclear reactions build heavier elements from lighter ones. Massive stars are important producers of oxygen. When stars release material, that oxygen can enter the gas from which later stars form. Explosions called supernovae also release enormous energy. Along with energy from massive stars, they can drive streams of gas outward. These flows are known as galactic winds. This creates a question about a galaxy’s history. How much material has it made, how much has it kept, and how much has left? Oxygen is useful for answering it because astronomers can detect it and estimate its production by stars. The GLOW project examines these flows in small galaxies. Hubble can distinguish individual stars in the nearby sample. Their colours and brightness help researchers reconstruct when stars formed. Combining that history with measurements of gas and chemical composition allows a comparison between oxygen production and retention.

How it developed

2 November 2026

How it started
The oxygen inventory challenges predictions about small galaxies

The GLOW team combined archival Hubble images with observations from Spitzer and ground-based radio telescopes. It examined oxygen in stars, gas and dust, finding that most of the retained oxygen was in gas. The measurements suggest that outward gas flows remove oxygen more effectively than the models predict. Researchers now want to understand how much remains around each galaxy and how much travels farther. Future observations of even smaller galaxies could help test how this process varies with a galaxy’s size and surroundings.

NASA GLOW research team / arXiv Rutgers University

Why it matters for UPSC

GS3 · Space researchGS3 · Scientific methods

For GS3, connect stellar element formation, supernovae and galaxy evolution. Explain how observations test a computer model. Distinguish the measured oxygen remaining in galaxies from the inferred amount carried away.

Key terms

Dwarf galaxyA galaxy with far fewer stars and much less mass than a large galaxy such as the Milky Way. Nearby examples allow telescopes to distinguish individual stars. This makes them useful for reconstructing how galaxies formed stars and exchanged gas over time.

Stellar nucleosynthesisThe formation of chemical elements through nuclear reactions in stars. It explains how stars produce oxygen and other elements. Studying the stars’ history helps scientists estimate how much oxygen a galaxy should have produced.

SupernovaA powerful stellar explosion that releases energy and material into surrounding space. That energy can help drive gas out of a galaxy. Supernovae therefore influence both the spread of elements and the gas available for later star formation.

Galactic windA large-scale outward flow of gas from a galaxy. Energy from massive stars and supernovae can drive it. The flow can carry elements such as oxygen into the gas surrounding the galaxy or farther into space.

Circumgalactic mediumThe thin gas surrounding the main body of a galaxy. Some expelled material can remain in this region or later return. Researchers are investigating how much of the missing oxygen in the GLOW sample is stored there.

Computer simulationA calculation that uses physical rules and assumptions to model how a system changes. Astronomers compare its predictions with observations. A mismatch, such as unexpectedly low oxygen retention, helps identify processes that the model needs to describe better.

Sources (3)

NASA · official · Hubble uncovers missing oxygen in nearby dwarf galaxies3 Nov, 8:19 pm
GLOW research team / arXiv · official · GLOW II: A Census of Oxygen in Low-Mass Galaxies3 Nov, 8:19 pm
Rutgers University · official · Stars Make Oxygen for Small Galaxies. They Lose Most of It.3 Nov, 8:19 pm