Distant galaxy reveals oldest stars ever found

Mindy Sparks
May 17, 2018

The stars pumping out oxygen in MACS1149-JD1 are calculated to be approximately 13.3 billion years old, so around 500 million years after the Big Bang, but naturally to reach a stage of emitting oxygen they must have formed much earlier - about 250 million years earlier, say the worldwide team of astronomers who spotted them.

The galaxy's "red shift", a measurement technique that shows the distance to - and the age of - astronomical objects, was determined to be 9.1096, the largest value ever detected to date using spectral line analysis, the publication said.

Pinning down the star formation history of the Universe is a challenging task, but astronomers studying the very distant galaxy MACS1149-JD have detected the most distant oxygen ever detected from stars that had begun forming a mere 250 million years after the Big Bang. This is exceptionally early in the history of the universe and suggests that rich chemical environments evolved quickly.

An worldwide team of researchers from University College London and Osaka Sangyo University in Japan published a paper in the journal Nature showing that stars in the MACS1149-JD1 galaxy formed 250 million years after the Big Bang.

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.

After they were liberated from their stellar furnaces by supernovas, these oxygen atoms made their way into interstellar space. The massive newborn stars in the second burst ionize oxygen, and it's those emissions that have been detected with ALMA. This also broke their own record for finding the most distant source of oxygen. This distance estimate was further confirmed by observations of neutral hydrogen in the galaxy by the European Southern Observatory's Very Large Telescope.

The study authors conclude "it may be possible to detect such early episodes of star formation in similar galaxies with future telescopes". The model indicates that the star formation became inactive after the first stars ignited.

It can take millions of years for signals to travel across space. Oxygen is only created in stars and then released into the gas clouds in galaxies when those stars die. They measured the frequency of a peak in the galaxy's spectrum that comes from ionized oxygen gas. For this reason, the presence of distant oxygen is a sign there were earlier generations of stars in this galaxy, an emailed press release on the study reported. "We are therefore able to use this galaxy to probe into an earlier, completely uncharted period of cosmic history", Nicolas Laporte, a researcher at University College London (UCL) in the United Kingdom and second author of the new paper, explained in the statement.

Galaxy MACS1149-JD1 is 13.28 billion light years away and contains the most distant detection of oxygen, which could indicate stars which have already completed their life cycle. ALMA has been used previously to break the record for the most distant known galaxy, it did so twice in 2016 finding galaxies 13.1 billion light-years away, and 13.2 billion light-years away. 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. "We are eager to find oxygen in even farther parts of the universe and expand the horizon of human knowledge".

The study, published today in the journal Nature, was an worldwide and collaborative effort.

The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.

[2] The galaxy GN-z11 is thought to be located 13.4 billion light-years away based on observations with the Hubble Space Telescope (HST).

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