Ancient galaxy holds oldest oxygen in universe
NAOJ

Ancient galaxy holds oldest oxygen in universe

One of the oldest known galaxies in the universe is now home to the oldest oxygen yet spotted, a new study suggests. That massive group of stars, dubbed SXDF-NB1006-2, lies about 13.1 billion light-years from Earth and was the oldest known galaxy when it was discovered in 2012 (a record that has been toppled several times since). When first observed, astronomers also discerned that the galaxy had a halo of ionized hydrogen (purple in the artist’s sketch above), a sign that radiation streaming from the galaxy’s stars was energetic enough to strip electrons from atoms in that region of space. Now, new observations of a particular wavelength of infrared light from that galaxy betrays the presence of oxygen atoms that have two electrons missing (in the smaller region depicted in green), researchers report online today in Science. Because all elements in the universe heavier than hydrogen, helium, and lithium have been forged by nuclear fusion in the cores of stars and then scattered into space by supernova explosions, the find indicates that the galaxy, at the age we’re now observing it, was old enough for at least one generation of stars to have formed, lived, and died. The lack of infrared glow from the galaxy across a broad range of wavelengths, however, suggests that there’s very little dust there to absorb and then re-radiate the stars’ radiation, the team notes. There are likely many other galaxies of the same age sporting haloes of oxygen, the team notes, and detecting and then analyzing them will help shed light on how stars and galaxies formed and evolved in the early universe.