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Scientists detect oxygen legacy of first stars

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Distant galaxy hints at universe's earliest stars

The galaxy, MACS1149-JD1, is 13.28 billion light years away and contains the most distant detected source of oxygen. Oxygen distribution is shown in red.

The discovery could provide more information on how the early universe looked like.

This research is presented in a paper "The onset of star formation 250 million years after the Big Bang", by T. Hashimoto et al., to appear in the journal Nature. When that light was produced in MACS1149-JD1 it was in the infrared, but during its billions of years journeying to Earth, the expansion of the universe stretched it out to the microwave frequencies that ALMA is sensitive to.

The oxygen in MACS1149-JD1 by definition therefore has to reach back to a time earlier than it is being seen. Within the galaxy, the team was surprised to discover faint signals of ionized oxygen that were emitted nearly 13.3 billion years ago (or 500 million years after the Big Bang).

Atacama Large Millimeter/submillimeter Array (ALMA) and ESO's Very Large Telescope (VLT) have captured the evidence on star formation in the very distant galaxy MACS1149-JD1 suggesting that the formation started at an unexpectedly early stage, only 250 million years after the Big Bang.

"This has very exciting implications for finding "cosmic dawn" when the first galaxies emerged", adds Nicolas Laporte, a researcher at University College London/Université de Toulouse and a member of the research team.

In addition to the glow from oxygen picked up by ALMA, a weaker signal of hydrogen emission was also detected by VLT.

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The researchers confirmed the distance of the galaxy with observations from ground-based telescopes in Chile and reconstructed the earlier history of MACS1149-JD1 using infrared data from orbiting telescopes. "This detection pushes back the frontiers of the observable Universe", said Dr. Takuya Hashimoto, an astronomer at both Osaka Sangyo University and the National Astronomical Observatory of Japan.

Scientists have determined this measurement based on lines in the ionized oxygen spectra, rather than employing ionized carbon, which is more commonly used when scanning faraway space objects.

Richard Ellis, a senior astronomer at UCL and co-author of the paper, concludes: "Determining when cosmic dawn occurred is akin to the Holy Grail of cosmology and galaxy formation".

"Oxygen is only created in stars and then released into the gas clouds in galaxies when those stars die", said a UCL statement.

The "redshift" of the galaxy, a measurement that establishes the age and distance of a space object, was 9.1096 units, the biggest value obtained so far from the study of spectral lines, as revealed by the report for this study. The MACS1149-JD1 observation shows galaxies must have existed before any that are now detectable. There is renewed optimism we are getting closer and closer to witnessing directly the birth of starlight.

'Since we are all made of processed stellar material, this is really finding our own origins'.

"Prior to our study, there were only theoretical predictions of the earliest star formation".

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