Astronomers have discovered a distant galaxy that formed in the early universe, resembling a cluster of grapes, thus nicknamed “Cosmic Grapes.” This discovery far exceeds astronomers’ expectations for galaxies in the early universe.
Through the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile and the James Webb Space Telescope (JWST) of NASA in the United States, astronomers have found this primitive galaxy enhanced by the effects of gravitational lensing.
Formed 9.3 billion years after the Big Bang, this galaxy existed during the early universe. It consists of at least 15 dense clumps of stars embedded in a rotating disk, resembling “Cosmic Grapes.”
The sizes of these “grapes” range from 10 to 60 parsecs (1 parsec is about 3.26 light-years). They emit ultraviolet light, accounting for 70% of the entire galaxy, reshaping our understanding of the structure formation of early galaxies.
Astronomers observed this galaxy for over 100 hours, making it one of the most in-depth studies of early galaxies in the universe.
While previous observations with the Hubble Space Telescope depicted the galaxy as a smooth single disk, the powerful resolution of ALMA and JWST, along with the enhanced gravitational lensing effect, reveal a completely different “grape-like” appearance of the galaxy.
Lead author of the study, Seiji Fujimoto, who previously worked at the University of Texas at Austin and currently works at the University of Toronto in Canada, stated in a news release, “This object is considered one of the galaxies with the strongest gravitational lensing effect among the distant galaxies discovered so far.”
Fujimoto further added, “Due to this powerful natural amplification effect paired with observations from some of the world’s most advanced telescopes, we have a unique opportunity to study the internal structure of distant galaxies with unprecedented sensitivity and resolution.”
This discovery marks the first time astronomers have linked the small-scale internal structure of typical early universe galaxies with large-scale rotation, achieving a spatial resolution of just 10 parsecs.
This galaxy is not a rare or extreme system. In terms of stellar formation activities, mass, size, and chemical composition, it lies precisely on the “main sequence” of galaxies, indicating it likely represents a broader population.
If this is the case, many other galaxies currently observed that appear smooth may be composed of similar unobserved substructures, which are currently beyond the resolution of telescopes to reveal their true nature.
As existing simulations cannot reproduce such a large number of clumps in rotating galaxies in the early universe, this discovery poses key questions about how galaxies form and evolve. This suggests that our understanding of feedback processes in young galaxies and the formation of structures may require significant revisions.
“Cosmic Grapes” have opened a unique window for understanding the birth and development of galaxies, perhaps being just the first of many such galaxies. Future observations will be crucial in uncovering whether this clumpy structure in the early universe is prevalent.
The above research findings were published on August 7 in the journal “Nature Astronomy.”