When you think about a galaxy, you most likely picture a spiral galaxy like the Milky Way, however spirals make up only about 60% of the galaxies we see. Thats due to the fact that spiral galaxies only form when smaller galaxies combine and collide over time. The authors were careful to keep in mind that some might be combining galaxies that were misclassified, however even then 108 of the galaxies were unanimously classified as spirals by critics. When the group adjusted observations, they discovered about a fifth of galaxies at z = 3 are spiral galaxies. With future data from JWST, the team hopes to identify just how these early galaxies develop, and why spiral galaxies have actually been around for so long.
The standard model of galaxies is that they progress over time. Galaxies formed from vast clouds of primordial hydrogen and helium, therefore most likely had a fairly amorphous structure at the beginning. Offered the density of the early Universe, galactic collisions and mergers were common, which provided galaxies their rotations and caused them to form disks and spirals. All of this takes some time, so we would expect spiral galaxies to be relatively common in the local Universe, however rare in the early Universe.
This brand-new work utilized information from the Cosmic Evolution Early Release Science Survey (CEERS), which was collected by the James Webb Space Telescope. The group identified 873 galaxies higher than 10 billion solar masses, with redshifts between z = 0.5 and z = 4. Galaxies at this redshift are in between 5 billion and 12 billion years old, so they span the variety of early galaxies to contemporary ones.
The portion of spiral nebula as a function of redshift. Credit: Kuhn, et al
. Of these galaxies, 216 were classified as spirals. The authors were careful to keep in mind that some may be combining galaxies that were misclassified, but even then 108 of the galaxies were all categorized as spirals by critics. When the team organized them by redshift, they discovered that while the portion of spirals reduced as you went further into the past, the fraction of spirals at redshifts above z = 3 was much higher than anticipated. When the group calibrated observations, they found about a fifth of galaxies at z = 3 are spiral galaxies. These really early galaxies would have needed to end up being spirals less than 2 billion years after the Big Bang, indicating that there would have been little time for mergers and collisions to be the cause.
In other words, many galaxies evolved into disk-shaped spirals quite early in the Universe. So while accidents and mergers do contribute in the development of spiral nebula, there are most likely other aspects that come into play. At the minute it isnt clear what those factors are. With future data from JWST, the team hopes to figure out just how these early galaxies develop, and why spiral galaxies have actually been around for so long.
Referral: Kuhn, Vicki, et al. “JWST Reveals a Surprisingly High Fraction of Galaxies Being Spiral-like at 0.5?
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When you believe about a galaxy, you most likely think of a spiral galaxy like the Milky Way, but spirals make up just about 60% of the galaxies we see. Thats because spiral galaxies just form when smaller sized galaxies collide and merge over time.
