Astronomers detect most distant oxygen signature

The signature of faraway ionized oxygen may help researchers determine which cosmic objects triggered reionization shortly after the Big Bang.

By Brooks Hays
Astronomers detect most distant oxygen signature
Color composite image of SXDF-NB1006-2. Light from ionized oxygen detected by ALMA is shown in green. Light from ionized hydrogen detected by the Subaru Telescope and ultraviolet light detected by the UK Infrared Telescope (UKIRT) are shown in blue and red, respectively. Credit: ALMA (ESO/NAOJ/NRAO), NAOJ

TOKYO, June 16 (UPI) -- Astronomers in Japan have identified oxygen 13.1 billion light-years away. Scientists located the element's signature in the faraway galaxy SXDF-NB1006-2 using the Atacama Large Millimeter/submillimeter Array.

Faraway galaxies offer astronomers to look back in time to see what the universe looked like not long after the Big Bang, when heavier elements like oxygen were rare.


"Studying heavy elements also gives us a hint to understand how the galaxies were formed and what caused the cosmic reionization," Akio Inoue, a researcher at Osaka Sangyo University, explained in a news release.

Cosmic reionization was a reheating of the universe that followed a period of cooling -- cooling that allowed the universe's material to begin to coalesce into gas and dust clouds, collapsing to form the first stars and galaxies. The energy from these first cosmic objects ionized neutral gas like hydrogen.

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Prior to the reionization, the universe was mostly opaque -- scattered protons and free electrons absorbing most of the universe's light. The ionization of hydrogen allowed light to travel through a much more transparent universe. Cosmic reionization was key in creating the universe we know today, but scientists haven't been able to confirm what exactly set it in motion.


The signature of ionized oxygen, like the one detected by ALMA, may help researchers determine which objects triggered reionization.

There isn't much of the newly detected oxygen in SXDF-NB1006-2, as star formation was a relatively new phenomenon 13.1 billion years ago. But scientists can tell from their analysis of the oxygen that the galaxy hosts several giant stars putting out intense ultraviolet radiation.

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Researchers believe most of the gases found in SXDF-NB1006-2 will be highly ionized, which would suggest it and galaxies like it played an important role in cosmic reionization.

"This is the first step to understanding what kind of objects caused cosmic reionization," said Yoichi Tamura, an astronomer at the University of Tokyo. "Our next observations with ALMA have already started. Higher resolution observations will allow us to see the distribution and motion of ionized oxygen in the galaxy and provide precious information to understand the properties of the galaxy."

The researchers detailed their latest discovery in the journal Science.

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