The James Webb Space Telescope (JWST) has revealed oddly shaped galaxies in the early universe that are helping astronomers solve the mystery of why some young galaxies appear to be filled with mature stars.
Surfboard and Pool Noodle Shaped Galaxies Spotted by Webb
The JWST peered back in time over 13 billion years and spotted massive disky galaxies swirling together and merging to form new galaxies. But strangely, many of these early galaxies had elongated shapes described as looking like “thin disks, gently warped pool noodles, and even complete sprial arms” (source).
“Their shapes are very unexpected. We’ve never seen anything like them. These 18 objects astonished me when we first saw the images” said astronomer Joel Leja (source).
Some examples captured by Webb:
| Galaxy Name | Description |
|---|---|
| GN-z9-Webb-1 | Shaped like a thin disk or gently bent surfboard |
| GN-z9-Webb-2 | Spiral shaped like a twisted pool noodle |
| GN-z9-Webb-3 | Football-shaped with spiral arms |
These oddly shaped galaxies challenge our understanding of how galaxies formed in the early universe. Based on our current models, young galaxies shortly after the Big Bang should have chaotic shapes and contain mostly young populations of stars. But many of these galaxies had orderly, mature-looking shapes.
“The morphologies of these galaxies are much more orderly than we expected” said astronomer Erica Nelson (source). This raises the question – how did these early galaxies become so neat and structured so quickly after the Big Bang?
Mature Stars Found in Young Galaxies
Webb also spotted mature stars in many of these young galaxies. These galaxies existed just 650-900 million years after the Big Bang, not nearly enough time for successive generations of stars to form and expire. Yet they were filled with old stars.
“The galaxies are so bright, we shouldn’t be able to see the light from their older stars” said Nelson (source). The old stars indicate the galaxies grew up much faster than expected.
Some theories suggested supermassive black holes were swallowing loads of gas and spewing out radiation that encouraged rapid star formation. But Nelson found no evidence for that. “We don’t see any heavy elements that those supermassive black holes should have spat out” she said (source).
Galaxy Mergers Solved the Mystery
Another Webb observation finally revealed the solution to this mystery of unexpectedly bright and neat young galaxies full of old stars.
Webb spotted two galaxies on the brink of merging together into one galaxy. The galaxies were rich with surprisingly high amounts of ionized hydrogen – the mysterious sign of rapid star formation.
As the two galaxies gravitationally pulled each other together, their gas clouds collided at high speeds, compressing the gas and triggering intense bursts of new star formation (source). This rapid star formation lit up the galaxies with unusually bright light.
“We’re seeing the actual formation of hydrogen before, during, and after galaxies collide. We have never been able observe such details of hydrogen during the epoch of galaxy formation” said astronomer Hashima Hasan (source).
The observation supports the theory that the oddly bright and neat young galaxies were created by mergers of smaller galaxies coming together. The galaxy collisions triggered exceptionally efficient star formation that quickly built up huge galaxies full of prematurely old stars.
“Now we know why certain galaxies we observe from this ancient era are so massive and mature looking – galaxy mergers had accelerated their growth early on” said Nelson (source). Mystery solved!
More Webb Discoveries About Early Galaxies Ahead
The recent Webb discoveries have overturned many assumptions about how galaxies formed shortly after the Big Bang. Webb program manager Klaus Pontoppidan said “astronomers will now have much to do as they analyze Webb’s full set of long exposure images of early galaxies” (source).
There are likely more surprises in store about the chaotic early years of galaxy formation. Nelson says her team has much more analysis to do, but she promised Webb would continue revealing the evolution of galaxies over cosmic time: “Stay tuned for more results!” (source).
What This Means for Understanding Galaxy and Star Formation
The recent Webb observations have enormous implications for theories of galaxy formation. Previously, models assumed primordial gas clouds gradually coalesced into galaxies and then slowly formed stars. But Webb revealed galaxies actually grew much faster due to rapid bursts of star formation triggered by violent galaxy collisions.
This indicates classic theories of galaxy assembly need major revisions. Pontoppidan said “imagers and theorists will be busy trying to piece together how these galaxies formed in the early universe” (source). The new Webb images will help guide simulations and models to better match the unexpected reality of runaway starbursts and premature galaxy growth.
With more observing time, Webb can spot even more infant galaxies in their formation stages. Each new observation adds crucial data points to trace out the full history of how galaxies came together and filled up with stars after the first cosmic dawn.
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