Odest oxygen in the universe has been spotted in an ancient galaxy, 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, 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, researchers said.
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 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.
Before planets, stars and galaxies began to take shape; the Universe was filled with electrically neutral gas. Several hundred million years after the Big Bang, the first stellar objects began to shine. This phase is known as cosmic reionization. And it broke up neutral atoms and ionized the gas.
Astronomers from across the world continue to debate exactly what kind of objects are responsible for this phase. Training the most powerful telescopes on Earth to the most distant galaxies helps us get closer to an answer.
When SXDF-NB1006-2 was first discovered in 2012, it set the record for the most distant galaxy ever observed. That record didn’t stand long and continues to be broken each year. But the galaxy was still a great candidate to search for heavy elements such as oxygen and carbon.
Observing SXDF-NB1006-2 with ALMA brought its own non-traditional challenges. Astronomers from across the world vie for time with the best telescopes. Inoue and the rest of the team turned to computer simulations to predict how easily an oxygen detection would be for ALMA to see. The results showed the oxygen emission should be easily detected.
With the coveted time to use ALMA secured, the astronomers observed the galaxy and detected just what they predicted – light from ionized oxygen. And with it, concrete evidence that oxygen existed just 700 million years after the Big Bang.