A Twin of the Milky Way in the Young Cosmos Raises Questions

Recent observations from the James Webb Space Telescope (JWST) have unveiled a surprising discovery: a spiral galaxy resembling our Milky Way existed just one billion years after the Big Bang. This finding contradicts previous theories that suggested the formation of spiral galaxies would take billions of years.

The international research team, which reported their findings in the journal Astronomy & Astrophysics, highlighted that while the JWST has identified numerous galaxies formed 300 to 500 million years after the universe began, these were typically small and irregular in shape. The prevailing theory among astronomers posits that larger galaxies, such as spiral galaxies, evolve over time through collisions and mergers of smaller dwarf galaxies.

The newly discovered galaxy, named Zhulong after a dragon from Chinese mythology, has a diameter of approximately 60,000 light-years and houses over 100 billion stars, comparable to the Milky Way. Zhulong exhibits a central bulge of older stars, encircled by a flat disk with spiral arms where new stars are actively forming.

This revelation raises significant questions about how a galaxy of such complexity and structure could have formed so early in cosmic history. Mengyuan Xiao from the University of Geneva noted that the discovery challenges existing models regarding galaxy formation and development.

The team identified Zhulong during a project known as the Panoramic Survey, which scans random regions of the sky alongside other JWST observations. This approach allows researchers to uncover previously unknown objects in the early universe. Christina Williams, the lead scientist of the Panoramic Program, emphasized the potential of such parallel observations for discovering rare celestial objects.

These findings present a challenge to current theories on galaxy formation, and Xiao and colleagues aim to locate additional developed galaxies within the young cosmos through the Panoramic Program. They also plan to conduct further investigations of Zhulong using the Webb Telescope and the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to unravel the galaxy's formation history.