An international team of astronomers has announced the discovery of the oldest known spiral galaxy. It existed only a billion years after the Big Bang.
Large spiral galaxies, such as our Milky Way, are quite common in the local part of the Universe. But the closer we get to the time shortly after the Big Bang, the fewer they become. This is consistent with expectations, as large disk structures with spiral arms should have taken billions of years to form.
However, the new finding calls this claim into question and demonstrates that Milky Way-like galaxies may have existed in the universe much earlier than thought. This is about a discovery made by the James Webb Telescope (JWST) as part of the PANORAMIC survey. It managed to discover a spiral galaxy that existed just a billion years after the Big Bang. It is the most distant and oldest known spiral galaxy in the Universe.
The record-breaking galaxy was named Zhulong, after a deity from Chinese mythology who illuminated the darkness. It has a remarkably mature structure, unique to distant galaxies, which are usually irregularly shaped. It is similar to galaxies in the local universe, and has a mass and size similar to the Milky Way. Its structure shows a compact bulge in the center with older stars, surrounded by a large disk of younger stars that are concentrated in spiral arms.
Discovery is important for several reasons at once. First, it shows that mature galaxies like those in our neighborhood may have appeared much earlier than thought. Second, it has long been assumed that spiral arms take many billions of years to form. But Zhulong demonstrates that they can develop in a shorter time frame.
At the same time, given the fact that astronomers have not yet managed to find other galaxies similar to Zhulong in the early Universe, we can assume that spiral structures in those times were not characterized by longevity. Perhaps galactic mergers, or other evolutionary processes, destroyed them. Thus, spiral structures may be more stable in later periods of cosmic time, so they are more likely to be found in our neighborhood.
Future observations with JWST and ALMA should help astronomers confirm Zhulong’s properties and learn more about its formation history. As new large-scale studies continue, scientists expect to find even more such galaxies, which will provide new insights into the complex processes that shaped the early universe.
According to NOIRLab
