Astronomers discover oldest known spiral galaxy


The image below is an image of the oldest known spiral galaxy that scientists believe formed 12.4 billion years ago. The ancient galaxy is named BRI 1335-0417, and the image was taken by the Atacama Large Millimeter submillimeter Array (ALMA) telescope in Chile. The image is remarkable because it shows that spiral galaxies formed as early as 1.4 billion years after the Big Bang. Photographs like this are essentially a step back in time because we see it as it was over a billion years ago due to the time it took for its light to reach us.

Astronomer Dr Kai Noeske says the photograph shows that galaxies began to resemble modern galaxies about 1 billion years earlier than previously believed. Scientists say spiral galaxies are more mature forms of galaxies. In the early stages of a galaxy, dark matter gathers hot gases into clusters that create stars. The stars then merge to create larger galaxies which, at the start of their life, are distorted. Eventually the galaxies begin to rotate, creating disc-like shapes.

Spiral galaxies occur when these disks start to be disturbed. Noeske says that aside from looking pretty, the spiral arms also compress gas to become catalysts for new star formation. Currently, scientists believe that galaxy formation peaked around 3.3 billion years after the Big Bang, when most of the stars in the universe formed. It was a surprise that BIS 1335-0417 already had structures similar to nearby galaxies long before the active phase of galaxy formation. Before discovering BIS 1335-0417, the oldest known galaxy formed 2.5 billion years after the Big Bang.

This ages the BIS 1335-0417 by about 1 billion years. The new discoveries are changing scientific knowledge about how and when galaxies formed and evolved into what we see today. Astronomers note that while BIS 1335-0417 is the oldest known spiral galaxy, it is not the oldest galaxy ever observed. This title goes to a galaxy called GNz11 spotted last December that formed 13.4 billion years ago, barely 400 million years after the Big Bang.


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