Astronomers say they have discovered the oldest known spiral galaxy, which formed 12.4 billion years ago. The image below of this ancient galaxy, named BRI 1335-0417, was taken by the Atacama Large Millimeter Wave/Submillimeter Wave Array (ALMA) telescope in Chile. This image is noteworthy because it shows that spiral galaxies formed within 1.4 billion years of the Big Bang.
Astronomer Dr. Kai Noeske says the image shows galaxies began to resemble modern galaxies about a billion years earlier than previously thought. Scientists say spiral galaxies are the more mature form of galaxies. In the early stages of galaxies, dark matter holds hot gas together to form clumps of stars. These stars then coalesced to form larger galaxies that were warped and distorted early in their lives. Eventually, these galaxies began to rotate, forming a disk shape.
When these disk galaxies start to get disturbed, spiral galaxies emerge. In addition to their pretty appearance, the spiral arms compress gas and act as a catalyst for new star formation, Noeske said. Currently, scientists think galaxy formation peaked about 3.3 billion years after the Big Bang, when most of the stars in the universe formed. Surprisingly, BRI 1335-0417 already has a structure similar to that of nearby galaxies long before the active phase of galaxy formation. Before the discovery of BRI 1335-0417, the oldest known galaxies formed 2.5 billion years after the Big Bang.
This makes BRI 1335-0417 about a billion years older. The new discoveries have transformed scientific knowledge about how and when galaxies formed and evolved into the way we see them today. While BRI 1335-0417 is the oldest known spiral galaxy, it's not the oldest galaxy ever observed, the astronomers noted. That title belongs to a galaxy discovered last December called GNZ11, which formed 13.4 billion years ago, just 400 million years after the Big Bang.