If you ever want to get a bit of perspective, there’s very little that’s more humbling than a good deep field image – and JWST has just dropped a real showstopper.
In the latest image release, the powerful space telescope gazed back nearly 12 billion light-years into a tiny patch of sky, less than a fifth of the width of the full Moon. That little patch of sky is teeming with glittering lights.
It looks a lot like any patch of the sky seen when you look up from the ground on a cloudless night, with one major, jaw-dropping difference.
Most of the lights in the new JWST-Hubble composite image are not bright stars, but galaxies, stretching back almost as far across space-time as the beginning of the Universe.
You can tell the difference, because only the stars have the pointy diffraction spikes that are characteristic of a JWST image. This pattern is generated when light from a concentrated point source bends around the edges of the telescope. The light in galaxies is much less concentrated, so it doesn’t produce the same effect.
This makes it easy to identify foreground stars in JWST images, and tell them apart from background objects.
The focus of this particular image is a group of galaxies concentrated just below the center, glowing with a kind of golden light. The light from that group of galaxies has traveled for around 6.5 billion years to reach us – nearly half the 13.8 billion-year age of the Universe.
The observations were taken as part of the COSMOS-Web survey, a project aimed at cataloguing groups of galaxies to better understand the evolution of the Universe, which includes the cosmic web.
The distribution of galaxies throughout the Universe isn’t random or higgledy-piggledy; they organize themselves into clusters, connected by an invisible cosmic web of dark matter and hydrogen.
Combining JWST data with X-ray data from the Chandra X-ray Observatory reveals just how large this group is, the most massive identified in the view field. The hot gas that suffuses the cluster glows in X-radiation powerfully enough for Chandra to detect.
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There is, however, a lot more to be seen in the image, if you know how to look. In a catalog compiled from these data, an international team of astronomers led by astrophysicist Greta Toni of the University of Bologna has identified 1,678 groups of galaxies. Not 1,678 galaxies – 1,678 groups.
There is also nothing special about this little patch of sky, measuring just 6.44 by 6.44 arcminutes. The full Moon, for context, is around 30 arcminutes across. Every other tiny patch of sky should be just as teeming with galaxies, thousands upon thousands that can be imaged in an area smaller than your pinky nail.
If that’s not awe-inspiring, we don’t know what is.
If you want to remind yourself daily how small you are, you can download wallpaper-sized versions of the deep field on the ESA’s JWST website, and the most recent paper on Astronomy & Astrophysics.
