WASHINGTON DC. WA, November 3, 2026 — Using NASA’s Hubble Space Telescope to study close-by dwarf galaxies, astronomers have discovered a perplexing discrepancy between what is expected based upon theoretical models and what they observed. For the 37 dwarf galaxies studied, only a very small percentage of the oxygen that was supposedly produced by the stars in those galaxies still existed. This discovery, which was reported on earlier this week in The Astrophysical Journal, creates additional questions about how galaxies evolve throughout the history of the universe, published in astronomical journals.
Tracing an Element Back to Its Source
Oxygen is one of the main components that make up the interior of stars. Because oxygen is so common in stars, researchers can use it to determine the past of a galaxy. On the GLOW project (Galaxies Losing Oxygen via Winds), researchers were able to take advantage of Hubble’s resolution capabilities to view individual stars in nearby galaxies. This level of resolution enabled the researchers to recreate the star-forming activity that occurred in each of those galaxies, as well as estimate the amount of oxygen that should theoretically exist in each galaxy, tracked via space telescope archives.
The scientists also looked at the actual amount of oxygen that was present in the different parts of the galaxy (gas, stars and dust). On average across all samples, galaxies only retained approximately 11% of the oxygen that was estimated to be produced by its stars. Some galaxies retained as little as 4% and some as much as 25%, analyzed in galactic evolution studies.
Where Did the Missing Oxygen Go
Scientists think that stellar winds and supernovae are pushing oxygen from these small galaxies much quicker than what is predicted by our current models. Since dwarf galaxies have less gravitational pull than large galaxies, they are able to easily lose gas and other materials to surrounding space through energetic events. Researchers used data from the Hubble Space Telescope, NASA’s decommissioned Spitzer Space Telescope, the Very Large Array (VLA), and the Australia Telescope Compact Array (ATCA) to find out where the lost materials may have ended up, utilizing data from radio astronomy arrays.
The final destination of the missing oxygen remains unknown, despite there being several different data sources. A portion of the missing oxygen could be located within the diffuse gas which surrounds each galaxy (known as the circumgalactic medium). Another possibility is that the remainder of the missing oxygen has been completely removed from the galaxies and placed into the empty spaces between the galaxies. However, additional observations will need to be made to confirm this, monitored by astrophysical observatories.
A Mystery Bigger Than Expected
Researchers chose to study these particular 37 galaxies because they are at an intermediate mass scale, which is predicted by many theoretical models as having higher rates of oxygen loss via supernova-driven wind. In addition, these galaxies are located relatively close to us, allowing Hubble to image individual stars (something that would not be possible with more distant dwarf systems). Both factors combined to provide a unique opportunity to account for oxygen production and retention in detail.
Dr. Kristen McQuinn, the main scientist behind the research project, stated that the findings show the great amount of oxygen that can escape from galaxies. Dr. McQuinn also mentioned that scientists have known for quite some time that oxygen would have been present inside of those galaxies at some point during their histories. However, the current issue is finding out exactly how and where the oxygen left.
What Comes Next for the Research
The subsequent work of the research team will examine individual large stars in the selected galaxies that produce and release oxygen. Through closer study of these stars using Hubble, the research group believes it can gain a greater understanding of the precise processes causing oxygen to be lost from the galaxies. Such work would then enable the development of more accurate models for predicting galaxy chemical evolution.
Researchers find this research relevant to larger scales of the early universe as well as smaller scales such as the development of larger galaxies. By understanding how smaller galaxies lose their elements and how they are distributed, researchers can better understand how galaxies as a whole develop the chemical components needed to form stars and planets. Currently, the issue of missing oxygen continues to be studied by researchers globally, featured in scientific research portals.
