Distant galaxy reveals oldest stars ever found

Distant galaxy hints at universe's earliest stars

Researchers Close In On Birthdate of First Stars

This is not only the most distant detection of oxygen ever made by any telescope, but more importantly, the discovery of the ancient oxygen serves as clear evidence that stars began forming just 250 million years after the Big Bang, when the universe was less than 2 percent its current age. The discovery breaks the record for finding the most distant known source of oxygen. They found that the brightness of the galaxy would be very neatly explained by a model wherein the first stars formed 250 million years prior.

For a period after the Big Bang there was no oxygen in the Universe; it was created by the fusion processes of the first stars and then released when these stars died.

"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". The detection of oxygen in MACS1149-JD1 indicates that an earlier generations of stars had been already formed and expelled processed oxygen by the epoch of observation, which is only about 500 million years after the beginning of the Universe. The results will appear in the journal Nature on 17 May 2018.

"I was thrilled to see the signal of the distant oxygen in the ALMA data", says Takuya Hashimoto, the lead author of the new paper and a researcher at both Osaka Sangyo University and the National Astronomical Observatory of Japan. They detected a signal from ionised oxygen whose infrared light was stretched ten-fold to microwave wavelengths by the expansion of the Universe. This distance estimate was further confirmed by observations of neutral hydrogen in the galaxy by the European Southern Observatory's Very Large Telescope.

ALMA has set the record for the most distant oxygen several times. 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. Now, the two teams merged into one and achieved this new record.

"ALMA is now clearly the most powerful instrument for securing distances to galaxies in the early Universe ahead of the expected launch of the James Webb Space Telescope", commented Professor Richard Ellis, a co-author also at UCL. Photo: ALMA (ESO/NAOJ/NRAO), NASA/ESA Hubble Space Telescope, W. Zheng (JHU), M. Postman (STScI), the CLASH Team, Hashimoto et al.

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 global team of astronomers who spotted them. "This has very exciting implications for finding "cosmic dawn" when the first galaxies emerged", Laporte said in another statement, referring to the time when the earliest galaxies emerged from the complete darkness of the early universe.

By establishing the age of MACS1149-JD1, the team has effectively demonstrated the existence of early galaxies to times earlier than those where we can now directly detect them.

"Determining when cosmic dawn occurred is akin to the Holy Grail of cosmology and galaxy formation".

"We are therefore able to use this galaxy to probe into an earlier, completely uncharted, period of cosmic history". Whether MACS1149-JD1 is just an outlier or the tip of an iceberg will have to wait for more observations.

For MACS1149-JD1 to contain substantial amounts of oxygen, many stars must have already gone through that whole life cycle.

The Atacama Large Millimeter/submillimeter Array (ALMA), an global astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile.

Why is oxygen so significant?

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