Astronomers have made an exciting discovery—a massive spiral disk galaxy, much larger than expected, in the early universe.
This galaxy, called the ‘Big Wheel,’ is three times bigger than other galaxies from the same time period, challenging our current understanding of how galaxies form.
A surprising find in deep space
Disk galaxies, like our Milky Way, are flat, spinning structures filled with stars, gas, and dust. Scientists have long wondered how and when these disks form.
Now, a new study using data from the James Webb Space Telescope (JWST) has found a well-ordered disk galaxy that existed just 2.4 billion years after the Big Bang—much earlier than previously thought.
Dr. Themiya Nanayakkara, a galaxy expert from Swinburne University of Technology, was part of the international team behind this discovery. The research was published in Nature Astronomy and included scientists from around the world.
“Seeing such a huge, well-formed disk galaxy at this early stage of the universe makes us rethink how quickly and efficiently galaxies can grow,” says Dr. Nanayakkara.
The galaxy was spotted in a special region of space where a bright quasar (a super-bright galaxy core) exists at a redshift of z=3.25. This means we are seeing the galaxy as it was 11 billion years ago, just 2 billion years after the universe began.
Using two JWST instruments, NIRCam and NIRSpec, researchers analyzed the galaxy’s redshift, shape, and movement to confirm it was a large rotating disk.
“We found this galaxy by chance, but it turned out to be much bigger than expected,” says Dr. Nanayakkara. “Its radius is about 10 kiloparsecs (kpc), which is three times larger than what our current models predict.”
How did it get so big?
Further study using NIRSpec data revealed that the galaxy’s disk rotates at about 300 km per second, similar to the fastest rotating galaxies we see today. This makes the ‘Big Wheel’ the largest confirmed disk galaxy from this early period in the universe.
Scientists believe the galaxy formed in a dense environment full of gas, stars, and other galaxies, making it an ideal place for rapid disk growth. However, current computer models don’t fully explain how such an environment creates giant disks so early.
“To grow this fast, the galaxy must have had non-destructive mergers or gas inflows moving in the right direction,” explains Dr. Nanayakkara.
The area where the Big Wheel was found is part of a proto-galaxy cluster, a large structure with many galaxies and black holes. Scientists plan to study more galaxies in similar environments to understand how early disks formed.
“With more observations, we could find more giant disks from the early universe,” says Dr. Nanayakkara. “This could change our understanding of how galaxies like our Milky Way came to be.”
The discovery of the Big Wheel galaxy opens a new chapter in studying how galaxies formed in the early universe and shows that the cosmos may have built massive structures much faster than we ever imagined.
