The Webb Space Telescope is celebrating the New Year the same way we humans do, by taking pictures of bright flashes of color in the sky. Well, not exactly “in the sky” – Webb itself is a million miles away from Earth, and its targets are even further away. But a state-of-the-art space observatory has recently photographed two grand spiral galaxies, and one of them appears to be the most distant one yet identified.
The researchers have written papers on the two massive spiral galaxies, both of which are now posted on the arXiv preprint server. One of the ancient galaxies is named A2744-GDSp-z4; the other, even more distant, is called Zhúlóng, after the 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 distinct arms. Spiral galaxies with less distinct arms are called flocculent spiral galaxies. For reference, our Milky Way is a closed-sleeve spiral galaxy, although researchers continue to study its exact structure and what name best fits it.
A2744-GDSp-z4 (sorry, not a very funny nickname) can be seen below in Webb composite images. The galaxy weighs about 14 billion solar masses and has a surprisingly advanced structure for its age. The existence of the galaxy indicates that even 1.5 billion years after the Big Bang – i.e., at the beginning of the Universe – there were clearly defined spiral galaxies. While the spiral arms may not be entirely clear to our eyes, you can make out the general shape, especially in the far left image. The galaxy was found in the Abell 2744 galaxy cluster, one of Webb’s earliest scientific targets in which similar distant galaxies had previously been found.
Zhulong, pictured in pink at the top of the article, is “the most distant bulge+disk galaxy with spiral arms known to date,” the article says. 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 spiral of grand design generates only about 66 solar masses per year. This finding is interesting when combined with previous data from the Webb Telescope, which indicated that ancient galaxies were metal-poor and highly gaseous. Perhaps Zhulong, despite its size, did not have the necessary resources for faster star formation.
The magnificent spirals of grand design are extremely far away, which is why they look so pixelated in Webb’s images. Part of the reason Webb can see such distant objects is that it uses gravitational lenses-regions of space-time with such intense gravity that they bend light, allowing us to see objects behind them. When light is bent, it is refocused – magnified – for telescopes like Webb.
“Webb continues to revolutionize our understanding of the early universe and galactic evolution, and this is made possible by the telescope’s superior perception. “Webb can see through massive gas clouds that would otherwise block out the faintest and most distant light, allowing researchers to capture images of objects in the early Universe. Over the past two years, Webb has photographed galaxies that formed only a few hundred million years after the Big Bang, raising new questions about how these structures unfolded in the distant past.
