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The Webb Space Telescope is ushering in the New Year in a similar fashion to us humans, by capturing images of brilliant bursts of color in the sky. Well, not quite “in the sky”—Webb itself is a million miles from Earth, and its targets are much farther still. But the state-of-the-art space observatory has recently imaged two grand design spiral galaxies, and one appears to be the most distant yet identified.
Researchers wrote papers on the two massive spiral galaxies, both currently hosted on the preprint server arXiv. One of the ancient galaxies is dubbed A2744-GDSp-z4; the other—which is even more distant—is called Zhúlóng, after a red dragon deity in Chinese mythology. Both spiral galaxies are newly discovered and are grand design spiral galaxies, a type of spiral galaxy with very well-defined arms. Spiral galaxies with less defined arms are called flocculent spiral galaxies. For reference, our Milky Way is a barred spiral galaxy, though researchers continue to investigate its exact structure and what label best suits it.
A2744-GDSp-z4 (sorry, no fun nickname) can be seen below in composite images by Webb. The galaxy weighs in at around 14 billion solar masses and has a surprisingly developed structure for its age. The galaxy’s existence suggests that even 1.5 billion years after the Big Bang—which is to say, early in the universe’s existence—well-articulated spiral galaxies existed. Though the spiral arms may not be completely clear to our eyes, you can make out the general shape, particularly in the leftmost image. The galaxy was found in the galaxy cluster Abell 2744, one of Webb’s earliest scientific targets and which has previously yielded similarly distant galaxies.
Composite images of A2744-GDSp-z4 taken by Webb across several color bands. Image: Jain et al., 2024 Zhúlóng, pictured in pink at the top of this article, is “the most distant bulge+disk galaxy with spiral arms known to date,” according to the paper. It has a mass similar to that of the Milky Way (which is above average for such an early galaxy) and has a relatively low star formation rate. The grand-design spiral is only generating about 66 solar masses per year. That finding is interesting when paired with previous Webb telescope data that indicated ancient galaxies were metal-poor and very gassy. Perhaps Zhúlóng, despite its size, lacked the correct assets for a faster rate of star formation.
The superlative grand-design spirals are extremely far away, which is why they appear so pixellated in the Webb images. Part of the reason Webb can see such distant objects at all is that it makes use of gravitational lenses—regions of spacetime with such intense gravity that they bend light, allowing us to see objects behind them. When the light bends, it is refocused—magnified—for telescopes like Webb.
In other words, though the massive galaxies appear like smudges, the images are amazing, and Webb is functioning perfectly normally. Nearby galaxies imaged by the telescope are seen in much sharper relief. Below is a slider showing how Webb’s instruments reveal different aspects of a grand design spiral galaxy. The image on the left was taken by Webb’s Near-Infrared Camera, or NIRCam, while the image on the right was taken by MIRI, the telescope’s mid-infrared imager. NIRCam captures warmer light from newly formed stars, while MIRI captures the galaxy’s light that comes from cold grains of dust and gas. The galaxy shown here is much sharper than the ancient galaxies discussed in this article because it is much closer, at just 27 million light-years away.
Webb continues to shake up our understanding of the early universe vis-a-vis galactic evolution, an accomplishment made possible by the telescope’s remarkable perception. Webb can see through massive gas clouds that otherwise obscure the most faint and distant light, allowing researchers to image objects from the early universe. In the last two years, Webb has imaged galaxies that formed just a few hundred million years after the Big Bang and raised new questions about how those structures unfurled over deep time.
