NASA Hubble Study Finds Dwarf Galaxies Eject Most of Their Oxygen

What was announced

Astronomers using NASA’s Hubble Space Telescope published research in The Astrophysical Journal examining 37 nearby dwarf galaxies. These small galaxies contain between a few thousand and hundreds of millions of stars. The team measured oxygen levels across stars, gas, and dust as part of the Galaxies Losing Oxygen via Winds (GLOW) project, which received funding from NASA and the National Science Foundation.

The observations revealed that dwarf galaxies retain only a small fraction of the oxygen generated by their stars. Energy from massive stars and supernova explosions creates powerful galactic winds. These winds blow oxygen out of the galaxies and into intergalactic space much more efficiently than theoretical models had anticipated. The researchers combined archival optical data from Hubble with observations from the Spitzer Space Telescope, the Very Large Array, and the Australia Telescope Compact Array to make their calculations.

What it means

Oxygen is the most common element in the universe after hydrogen and helium. Because its production in stars is well understood and easy to measure, astronomers use oxygen to track how galaxies build up heavy elements over time.

The GLOW project demonstrates that low-mass galaxies act as major suppliers of chemical elements to the intergalactic medium, which is the space between galaxies. Previous research from 2014 established that larger galaxies like the Milky Way lose oxygen into surrounding gas haloes called the circumgalactic medium. This new study shows that even small galaxies drive heavy elements out into surrounding space, changing how astronomers model galaxy growth and chemical enrichment across cosmic time.

What the announcement does not tell us

The announcement does not confirm where the missing oxygen ultimately resides. It remains unclear whether the oxygen stays in the gas halo surrounding each dwarf galaxy or if the galactic winds launch it completely out of the galaxy's local environment.

The release also does not provide exact percentages for how much oxygen was expected versus how much was detected in the 37 galaxies. Additionally, the announcement mentions future observation programs using NASA's Nancy Grace Roman Space Telescope and James Webb Space Telescope, but it does not specify dates for when those projects will begin or release data.