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The Webb Space Telescope kicked off the New Year in a similar way to us humans, capturing images of brilliant bursts of color in the sky. Well, not quite “in the sky” – Webb himself is a million kilometers from Earth, and his targets are much further away. But the state-of-the-art space observatory has recently imaged two large design spiral galaxies, and one appears to be the most distant yet identified.
Researchers have written papers on both massive spiral galaxies currently host on the arXiv preprint server. One of the ancient galaxies is called A2744-GDSp-z4; the other – which is even more distant – is called Zhúlóng, after a red dragon deity in Chinese mythology. The two spiral galaxies are discovered again and are grand design spiral galaxya 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 galaxyalthough researchers continue to investigate its exact structure and which label fits best.
A2744-GDSp-z4 (sorry, not a funny nickname) can be seen below in the image composed by Webb. The galaxy weighs about 14 billion solar masses and has a surprisingly developed structure for its age. The existence of the galaxy suggests that even 1.5 billion years after the Big Bang – that is, before the existence of the universe – well-articulated spiral galaxies exist. Although 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 the first scientific objectives and that yielded first similar distant galaxies.
Zhúlóng, printed 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 spiral of grand design is generated only about 66 solar masses per year. That discovery is interesting when combined with previous Webb telescope data that indicated Ancient galaxies were metal-poor and gas-rich. Perhaps Zhulong, despite its size, lacked the correct assets for a faster rate of star formation.
The superlative spirals of grand design are very far away, which is why they look so pixelated in the Webb image. Part of the reason Webb can see such distant objects at all is that it makes use of it gravitational lenses– regions of space-time with such intense gravity that they bend light, allowing us to see objects behind them. When light bends, it’s refocused — magnified — by telescopes like Webb.
In other words, even if the massive galaxies appear as smudges, the images are amazing, and Webb works perfectly. 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 spiral galaxy of grand design. 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 infrared imager. NIRCam captures the hottest light from newly formed stars, while MIRI captures galaxy light coming 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, only 27 million light years away.
Webb continues to shake up our understanding of the early universe vis-à-vis galactic evolution, an achievement made possible by the remarkable perception of the telescope. Webb can see through massive gas clouds that otherwise obscure fainter, more distant light, allowing researchers to image objects in the early universe. In the last two years, Webb has image galaxies which formed only a few hundred million years ago after the Big Bang and raised new questions on how these structures have developed in deep time.
