Oxygen is only created in stars and then released into the gas clouds in galaxies when those stars die.
Its faint light has taken so long to reach Earth that its journey began just 500 million years after the Big Bang - the cataclysmic event that brought the cosmos into being.
There was also no oxygen in the early universe.
An global team of astronomers used ALMA to observe a distant galaxy called MACS1149-JD1. "It is truly remarkable that ALMA detected an emission line - the fingerprint of a particular element - at such a record-breaking distance". This period, commonly referred to as "cosmic dawn, ' is of particular interest because it marked the transition from a hot, dense, and almost homogeneous universe to the universe we are more familiar with today - one filled with stars, planets, nebulae, and people". They detected a signal from ionised oxygen whose infrared light was stretched ten-fold to microwave wavelengths by the expansion of the Universe.
It also breaks the record for the oldest oxygen ever detected, at 13.28 billion light-years away (500 million years after the Big Bang) - the smoking gun for that early star formation. This distance estimate was further confirmed by observations of neutral hydrogen in the galaxy by the European Southern Observatory's Very Large Telescope.
'There is renewed optimism we are getting closer and closer to witnessing directly the birth of starlight.
Pinpointing this period of star birth - which gave rise to oxygen, carbon and other elements in the Universe - is a holy grail for astronomers chasing down the beginning of everything.
A supernova occurs when a star explodes, shooting debris and particles into space. However, stars and their galaxies did not form immediately after the Big Bang. "We have for the first time observed the very early stage of star formation in the universe", said astronomer Takuya Hashimoto of Osaka Sangyo University in Japan. The gas then fell back into the galaxy leading to the second burst of star formation. The massive newborn stars in the second burst ionize oxygen, and it's those emissions that have been detected with ALMA.
"The mature stellar population in MACS1149-JD1 implies that stars were forming back to even earlier times, beyond what we can now see with our telescopes. This has very exciting implications for finding "cosmic dawn" when the first galaxies emerged" adds Nicolas Laporte, a researcher at University College London and a member of the research team. The presence of oxygen is a clear sign that there must have been even earlier generations of stars in this galaxy. In 2016, Akio Inoue at Osaka Sangyo University and his colleagues used ALMA to find a signal of oxygen emitted 13.1 billion years ago. Several months later, Nicolas Laporte of University College London used ALMA to detect oxygen at 13.2 billion light-years away. Both teams merged efforts to achieve this new record.
"With MACS1149-JD1, we have managed to probe history beyond the limits of when we can actually detect galaxies with current facilities", said Richard Ellis, another UCL co-author of the study.
Before the first stars kicked on, the universe was a relatively boring place, consisting primarily of radiation leftover from the Big Bang, as well as hydrogen and helium.
After that, objects in the Universe become progressively easier to see, and it's one of these that was the focus of an global team of astronomers, led by Takuya Hashimoto, an astronomer at Osaka Sangyo University and the National Astronomical Observatory of Japan.