Distant galaxy opens door to 'uncharted period of cosmic history'

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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.

The oxygen signal was observed from an ancient galaxy, MACS1149-JD1, which is the most distant galaxy observed yet.

The results demonstrate the usefulness of ALMA as a tool for measuring the red shift of distant galaxies, Rychard Bouwens, an astrophysicist at Leiden University, said in another article in Nature.

"This extremely distant, extremely young galaxy has a remarkable chemical maturity to it", says Wei Zheng, lead astronomer on the study. They measured the frequency of a peak in the galaxy's spectrum that comes from ionized oxygen gas. As this infrared light traversed space, the extension of the Universe extended it to wavelengths in excess of ten times longer when it achieved Earth and was identified by ALMA.

This image shows the galaxy cluster MACS J1149.5+2223 taken with the NASA/ESA Hubble Space Telescope; the inset image is the very distant galaxy MACS1149-JD1, seen as it was 13.3 billion years ago and observed with ALMA.

A team of astronomers using high-precision optical instruments were able to explore the galaxy under the code name MACS1149-JD1, which is considered the most remote from Earth, finding in it the presence of oxygen. According to Takuya Hashimoto, representing the Japanese University of Osaka, this invention allows to significantly extend the boundary of the Universe studied by scientists. While this ALMA study has indirectly dated that time to 250 million years after the Big Bang, the earliest direct detection was announced earlier this year, in the form of an ionized hydrogen signature hailing from when our universe was a mere 180 million years old.

After figuring out the age of the signal, the astronomers worked backwards to determine when the galaxy's first stars fired up. This makes MACS1149-JD1 the most distant galaxy with a precise distance measurement and the most distant galaxy ever observed with ALMA or the VLT.

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. The detection of oxygen in MACS1149-JD1 indicates that these earlier generations of stars had been already formed and expelled oxygen by just 500 million years after the beginning of the universe.

Scientists believe that the Universe's first stars formed in regions of very dense matter, although understanding of that process is still limited. "This has very exciting implications for finding "Cosmic Dawn" when the first galaxies emerged". By establishing the age of MACS1149-JD1, the team has effectively demonstrated that galaxies existed earlier than those we can now directly detect.

Richard Ellis, 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".