The discovery, made serendipitously through observations with the James Webb Space Telescope (JWST), revealed a disk galaxy from a time just two billion years after the Big Bang - roughly eleven billion years ago.

Dr Themiya Nanayakkara, a specialist in galaxy spectral modeling, explained that this find presents significant challenges to existing theories on the early formation of disk galaxies. "This galaxy not only challenges our existing models of early formation but also hints that dense, gas-rich environments may be the cradle for the universe's earliest giants," he said.

Dr Nanayakkara and the research team used data from two of JWST's instruments to pinpoint indicators of disk galaxies and analyze the structures within. Key metrics such as redshifts, morphology, and galactic movement were studied, leading to the identification of an unexpectedly large disk galaxy.

Named the 'Big Wheel', this galaxy has an optical radius of approximately 10 kiloparsecs - a size more than triple what current cosmological simulations suggest for galaxies of that epoch. "This galaxy, dubbed the 'Big Wheel' has an optical radius of around 10 kiloparsec, which is at least three times as large as what is predicted by current cosmological simulations," Dr Nanayakkara said.

Further examination using JWST data confirmed the galaxy's disk rotates at a speed of about 300 kilometers per second. It surpasses the size of any previously confirmed disk galaxy from this early period and rivals the dimensions of the largest spiral galaxies in the present-day universe.

Dr Nanayakkara noted that the Big Wheel resides in an extremely dense region of space, a setting that may promote early and rapid disk development. Current galaxy formation models rarely predict galaxies like the Big Wheel, indicating these over-dense conditions are not yet accurately incorporated into simulations.

"Environments of this kind are known to host frequent galaxy encounters, mergers and gas flows. Therefore, in order to have a disk form early and grow quickly, galaxy mergers in this environment must have been non-destructive and oriented in particular directions."

He further suggested that angular momentum from gas streams aligned with the galaxy's rotation could have facilitated the disk's formation.

This discovery opens new avenues for probing the early universe. Dr Nanayakkara and his colleagues aim to pursue more focused studies to build a larger dataset, which could redefine our understanding of the genesis and evolution of disk galaxies.

Swinburne was the sole Australian institution involved in the research effort.

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