Astronomers Confirm Detection of Oldest Galaxy Ever Observed

It has been estimated through observations and computer simulations that the universe likely contains something close to two trillion galaxies.

A galaxy nearly 13.5 billion light-years away has been confirmed as the earliest galaxy found to date.

Using the Atacama Large Millimeter/submillimeter Array (ALMA) astronomers were able to date the galaxy to just 367 million years before the big bang, confirming the discovery first made by the James Webb Space Telescope (JWST). The previous record holder for oldest observed galaxy was GN-z11, thought to have formed roughly 400 million years after the big bang.

The galaxy, named GHZ2/GLASS-z12 was first spotted in July 2022, not long after the JWST was turned on. The results were published in a paper in November but scientists wanted to confirm the results using another instrument.

ALMA pointed its 66 12-meter-long antennas at the galaxy and found an oxygen emission line close by. Follow-up analysis confirmed it was related to GHZ2/GLASS-z12.

Astronomers were looking for the emission because when light passes through oxygen, it is reemitted at a specific range of wavelengths. Oxygen is also created relatively quickly compared to most other elements, so it is often used to investigate distant galaxies.

“We performed detailed tests on the observations to confirm that this really is a robust detection, and it is very difficult to explain through any other interpretation,” Tom Bakx an astronomer at Nagoya University in Japan and one of the team leads at the National Astronomical Observatory of Japan said.

The slight variation of where the galaxy seems to be and the oxygen emission suggest that massive explosions when the galaxy formed may have pushed the oxygen out into intergalactic space. While intergalactic space is largely perceived as empty, with less than one atom of matter per square meter, the vast expanses between galaxies mean the matter between galaxies makes up an estimated 50 to 80% of all ordinary matter in the universe.

a Close up of the oldest observed galaxy, GLASS-z12 taken by the James Webb Space Telescope

© NASA . nasa

The team was able to use their tests to theorize that the galaxy formed elements heavier than hydrogen and helium relatively early. Hydrogen and helium are the most abundant elements in the universe and made up most of it before stars formed and started creating new elements by smashing atoms together in their cores. It is believed those elements remained locked inside stars until the first stars exploded, allowing them to spread across the universe.

That an early galaxy like GHZ2/GLASS-z22 had oxygen so early in the formation of the universe provides clues into the timeline of the first stars, which still have not been observed directly.

The big bang, theorized as the beginning of the universe, is thought to have occurred around 13.8 billion years ago. If true, it would mean that GHZ2-GLASS-z12 formed in its earliest days, just hundreds of millions of years after the big bang occurred.

“These deep ALMA observations provide robust evidence of the existence of galaxies within the first few hundred million years after the big bang, and confirm the surprising results from the Webb observations,” Jorge Zavala, Bakx’s co-lead at the National Astronomical Observatory of Japan, said.

“The combined power of Webb and the radio telescope array ALMA give us the confidence to push our cosmic horizons ever closer to the dawn of the Universe,” he added.