Hubble study shows dwarf galaxies lose most of their oxygen

NASA's Hubble Space Telescope has found that dwarf galaxies retain just about 11 percent of the oxygen produced by their stars, according to research led by the Space Telescope Science Institute in Baltimore, reported Mashable.

The study examined 37 nearby dwarf galaxies, which contain from a few thousand to hundreds of millions of stars. The most oxygen-efficient dwarf galaxies held onto about 25 percent, while the least retained only 4 percent of their oxygen.

Astronomers believe that supernova explosions generate winds strong enough to expel oxygen-rich gas from these galaxies, which have relatively weak gravity. Larger galaxies tend to retain three to four times more oxygen, earlier research has shown.

The project, called Galaxies Losing Oxygen via Winds (GLOW), tracks oxygen inside stars, in interstellar gas, and in the space between galaxies. Oxygen is used as a tracer because it is the most abundant element after hydrogen and helium and is relatively easy to measure.

The research team used Hubble's high-resolution images to study individual stars in the dwarf galaxies, determining their star formation histories and estimating how much oxygen should have been produced. They then measured the oxygen remaining, finding most oxygen resides in the gas rather than in stars.

The study also noted that a galaxy's location affects oxygen retention; those near larger galaxies or in crowded regions tend to lose more oxygen. The full findings were published in The Astrophysical Journal.