Discovery of Zhúlóng: A Gargantuan ‘Grand Design’ Spiral Galaxy
13.8 billion years ago, in the aftermath of the Big Bang, galaxies began to form from the cosmic chaos. However, a recent discovery challenges our understanding of how quickly these galaxies assembled. The James Webb Space Telescope (JWST) has identified a colossal galaxy named Zhúlóng, dating back to 12.8 billion years ago, showcasing intricate structures characteristic of grand design spiral galaxies.
Zhúlóng, named after the Torch Dragon of Chinese mythology, has been detailed in a study published in Astronomy & Astrophysics. According to astronomer Mengyuan Xiao of the University of Geneva in Switzerland, the presence of Zhúlóng indicates that mature galaxies emerged much earlier than previously believed, providing valuable insights into massive galaxy formation and the development of spiral structures in the early universe.
Grand design spiral galaxies, characterized by well-defined spiral arms extending from a central core, are considered the epitome of galaxy structure. While the origins of spiral galaxies remain unclear, they are rare in the early universe, with minimal presence beyond 11.5 billion years ago.
Zhúlóng was serendipitously discovered during JWST’s PANORAMIC survey, dedicated to observing galaxies in the Cosmic Dawn period. Despite the identification of other massive galaxies, Zhúlóng stands out for its evolved morphology, featuring a classical bulge, a star-forming disk, and grand-design spiral arms, all within just 1 billion years after the Big Bang.
Measuring 62,000 light-years in diameter with a mass comparable to the Milky Way, Zhúlóng bears striking similarities to our home galaxy in terms of size, shape, and stellar mass. Despite its massive size, the central black hole appears quiescent, indicating a slowdown in star formation activity.
Researchers believe Zhúlóng represents the earliest known example of a spiral galaxy, suggesting that Milky Way-like structures could form much faster than previously assumed, approximately 10 times quicker than in the present-day universe. This rapid formation and morphological evolution of massive galaxies in the early universe make Zhúlóng a truly exceptional discovery.
The groundbreaking findings on Zhúlóng have been documented in Astronomy & Astrophysics, shedding new light on the swift emergence of complex galaxy structures in the ancient cosmos.
An earlier version of this article was published in January 2025.
