Distant galaxy hints at universe's earliest stars

Rodiano Bonacci
Mag 16, 2018

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. Finding the earliest traces of these common elements would shed important light on the chemical evolution of galaxies, including our own.

Astronomers using some of the most powerful telescopes on Earth have found evidence that stars were forming incredibly early on in the life of the Universe - just 250 million years after the Big Bang, well before the proverbial dust had settled.

By detecting the most distant oxygen ever found, astronomers have shown that the first stars formed unexpectedly early.

That's when the Universe was just 2 percent of its current age - and a finding that breaks the previous record for evidence of early star formation.

In a new study set for publication tomorrow in the journal Nature, an worldwide team of astronomers used this impressive array to observe an extremely distant galaxy called MACS1149-JD1. He also is a member of the ALMA research team. However, numerous heavier elements we take for granted today (such as carbon and oxygen) did not exist before the first stars. These hot, ionized atoms then "glowed" brightly in infrared light.

Based on the wavelength of the light, stretched from infrared to microwave by the expansion of the Universe, the team ascertained that the galaxy is 13.28 billion light-years away.

This discovery also represents the most distant galaxy ever observed by the observatories that studied it; ESO's Very Large Telescope (VLT) and the Atacama Large Millimeter/submillimeter Array (ALMA) - an array that has already set the record for detecting the most distant oxygen several times before. This distance estimate was further confirmed by observations of neutral hydrogen in the galaxy by the European Southern Observatory's Very Large Telescope.

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

The team reconstructed the earlier history of MACS1149-JD1 using infrared data taken with the NASA/ESA Hubble Space Telescope and NASA Spitzer Space Telescope. The model indicates that the star formation became inactive after the first stars ignited.

According to this model, that first burst of star formation blew the gas away from the galaxy, which would have suppressed star formation.

It's the massive newborn stars from this second burst of star formation that would have ionised the oxygen left over from the first generation. Here, the oxygen distribution detected with ALMA is depicted in red. By establishing the age of MACS1149-JD1, the team has effectively demonstrated that galaxies existed earlier than those we can now directly detect.

"I was thrilled to see the signal of the distant oxygen in the ALMA data", Hashimoto said. In 2016, Professor Inoue and his colleagues detected oxygen emission at 13.1 billion light-years. 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 this discovery we managed to reach the earliest phase of cosmic star formation history", said Hashimoto. "We are eager to find oxygen in even farther parts of the universe and expand the horizon of human knowledge".

Titled "The onset of star formation 250 million years after the Big Bang", the paper, involving a large global team of researchers, was published online Wednesday in the journal Nature. "This detection pushes back the frontiers of the observable universe".

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.

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