Primordial Rotating Disk Composed of ≥15 Star Forming Clumps at Cosmic Dawn

Early galaxy formation, initiated by the dark matter and gas assembly, evolves through frequent mergers and feedback processes into dynamically hot, chaotic structures ¹ . In contrast, dynamically cold, smooth rotating disks have been observed in massive evolved galaxies merely 1.4 billion years after the Big~Bang ² , suggesting rapid morphological and dynamical evolution in the early Universe. Probing this evolution mechanism necessitates studies of young galaxies, yet efforts have been hindered by observational limitations in both sensitivity and spatial resolution. Here we report high-resolution observations of a strongly lensed and quintuply imaged, low-luminosity, young galaxy at z =6.072 (dubbed the Cosmic Grapes ), 930~million years after the Big Bang. Magnified by gravitational lensing, the galaxy is resolved into at least 15 individual star-forming clumps with effective radii of r _e ≃ 10-60 parsec (pc), which dominate ≃ 70% of the galaxy's total flux in rest-frame ultraviolet (UV). The cool gas emission unveils a smooth, underlying rotating disk (rotational-to-random motion ratio of 3.58 ± 0.74) characterized by a gravitationally unstable state (Toomre Q ≃ 0.2-0.3), with high surface gas densities comparable to local dusty starbursts with ≃ 10 ^3-5 solar mass (M _⊙ ) per pc ² . These gas properties suggest that the numerous star-forming clumps are formed through disk instabilities with weak feedback effects. The clumpiness of the Cosmic Grapes significantly exceeds that of galaxies at later epochs and the predictions from current simulations for early galaxies. Our findings have unveiled the connection between the host galaxy's internal small substructures and the underlying dynamics along with feedback effects for the first time at cosmic dawn, potentially explaining the high abundance of bright galaxies observed in the early Universe ³ .