Dwarf Galaxies Retain 10.7% of Their Stars’ Oxygen

A study of 37 nearby dwarf galaxies estimates that they retain an average of 10.7% of the oxygen their stars produced, leaving most of the estimated output outside the inventory measured within the galaxies. Individual retention estimates ranged from 4% to 25%, according to the researchers’ analysis published in The Astrophysical Journal. The research team reconstructed each galaxy’s history of star formation using images from the Hubble Space Telescope, which resolve individual stars. From those histories, the researchers estimated how much oxygen the stars had produced, then compared that total with oxygen measured in stars, gas and dust using data from other telescopes. Nearly all the oxygen accounted for in the inventory was in gas, according to the study’s account. Oxygen is produced inside stars and released into surrounding gas as stars evolve and die. Because it is relatively measurable, researchers use it to trace how elements made by stars are distributed within and around galaxies. Dwarf galaxies are of particular interest because their weaker gravity may make it easier for gas and elements to escape than in larger galaxies. The inventory does not establish where...