An image from NASA's Hubble Space Telescope, released on Nov. 2, 2026, shows the dwarf irregular galaxy NGC 4449. This object is part of a sample of 37 nearby dwarf galaxies — small galaxies containing a few thousand to hundreds of millions of stars — that a research team has analyzed with Hubble. The main finding of the study is that much of the oxygen the models expected to find in these galaxies is simply not there.

Dwarf galaxies are privileged laboratories for studying the chemical evolution of the universe: they are small systems with relatively simple star formation histories, where the production and dispersion of heavy elements such as oxygen should be easier to trace than in massive galaxies. That a significant fraction of the expected oxygen does not appear in the observed sample raises a mismatch between what chemical enrichment models predict and what is actually measured in these systems.

The work relies on observations from the Hubble Space Telescope, whose ability to resolve individual stars and gas regions in nearby galaxies makes it possible to estimate the abundance of elements such as oxygen in detail. NGC 4449, one of the galaxies in the sample, is a well-known dwarf irregular with a starburst, and serves as a reference for understanding the behavior of the set.

The discrepancy opened up by this study forces a reexamination of hypotheses about where the oxygen produced by stars in dwarf galaxies ends up: whether some of the enriched gas escapes the weak gravitational well of these systems, whether it is incorporated into phases of the interstellar medium that are hard to observe, or whether the stellar oxygen production models themselves need adjustments. The observations released by NASA do not yet detail which of these explanations the data favor, nor whether the team plans to expand the sample with future campaigns.