When did the first stars in the Universe form? This is a major conundrum in astronomy and cosmology, and a new study of a distant galaxy is helping to solve it.
Astronomers have detected ionised oxygen from star formation in a galaxy occurring just 250 million years after the Big Bang. It is the most distant oxygen ever detected.
The astronomers used the Atacama Large Millimeter/submillimeter Array and ESO’s Very Large Telescope (VLT) in Chile to study galaxy MACS1149-JD1.
A faint glow of ionised oxygen was detected in the galaxy.
As this infrared light beamed across the cosmos to reach Earth, the expansion of the Universe caused it to stretch it to wavelengths over ten times as long.
This ‘signal’ was emitted 13.3 billion years ago, just 500 million years after the Big Bang, and the presence of oxygen is evidence that there may have been earlier generations of stars within the galaxy.
Astronomers believe that shortly after the Big Bang, there was no oxygen in the Universe.
Oxygen was later formed by the fusion processes of the first stars, and then released when those stars died.
Unit Telescope 4 of the Very Large Telescope in the Chilean Atacama desert. Perfect dark skies for observing the early Universe. Credit: F. Char/ESO
The fact that the stars in MACS1149-JD1 are so old adds another piece to the puzzle as to when the first galaxies emerged in the Universe. This period as known as the ‘cosmic dawn’.
This latest research suggests that galaxies existed even earlier than thought.
“This galaxy is seen at a time when the Universe was only 500 million years old and yet it already has a population of mature stars,” says Nicolas Laporte, a researcher at University College London (UCL) and second author of the paper.
“We are therefore able to use this galaxy to probe into an earlier, completely uncharted period of cosmic history.”