Astronomers at the University of Milano-Bicocca have identified a massive spiral galaxy, named "Big Wheel", which formed approximately two billion years after the Big Bang. The galaxy is one of the largest found from such an early period in the universe’s history.
Big Wheel is located 11.7 billion light-years from Earth and was observed near a quasar using the James Webb Space Telescope’s (JWST) Near-Infrared Spectrograph (NIRSpec). Quasars are active galactic nuclei powered by supermassive black holes.
The galaxy spans around 100,000 light-years and is estimated to be five times more massive than the Milky Way. Its significant scale is unusual for the time it existed, as most galaxies from that period are generally small and less developed.
Spectroscopic data from JWST confirmed that Big Wheel has a rotating disk structure. The rotation curve is flat, similar to what is observed in well-formed spiral galaxies today, indicating mature galactic dynamics despite its early formation.
Big Wheel's rotation speed follows the Tully-Fisher relationship, a modern correlation between galaxy rotation and luminosity. This further supports its classific
The galaxy is located in a high-density region where galaxy numbers are more than ten times the cosmic average. This environment likely enabled rapid mass accumulation and disk formation through gas accretion and mergers with other gas-rich galaxies.
The presence of Big Wheel challenges existing models of galaxy formation, which typically assume slower, gradual development. Researchers suggest that early massive galaxies may form rapidly in dense regions, prompting future revisions in cosmological theories. The study was published on 17 March in Nature Astronomy.