Recently, scientists discovered the earliest spiral galaxy ever seen — imaging it as it looked when the universe was only two-and-a-half billion years old. They think this galaxy might be one of the first of its kind, representing the beginning of the era of disk galaxies.
Unlike their cousin elliptical galaxies, which can look like homely blobs by comparison, spiral galaxies have spinning arms and bars filled with brilliant star formation. For over 50 years, scientists have been debating how spiral galaxies are formed, and if they can maintain their figures over the long term.
With the new data, the title of earliest spiral galaxy now goes to
A1689B11, which, after galaxy Q2343-BX442, is only the second spiral galaxy to be found within the first 3.3 billion years of the universe’s life.
At 2.5 billion years, the universe seems to have been mostly filled with clumpy and irregular galaxies, but just one billion years later, spiral galaxies are commonly found. Today over 70 percent of galaxies have spiral arms. Scientists are debating whether this age boundary is an effect of observing limits, or the result of a physical mechanism in the early universe.
The galaxy, in addition to its record-breaking status, has a peculiar mash-up of characteristics. It’s a prodigious star former, creating new stars at a rate 20 times higher than galaxies today — a characteristic common to many early galaxies — but it also has a cool, thin disk with little turbulence — something seen rarely in galaxies of that epoch.
“This is just one galaxy — it could be an outlier. Once we have more, we’ll know if it’s common or special,” says Tiantian Yuan, lead author on the study and astronomer at Swinburne University of Technology in Melbourne, Australia. “We need to look into the early universe to see if there are sufficient conditions to form arms.”