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Webb uses a galactic megacluster as an enormous magnifying lens

Georgina Torbet
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Modern space telescopes are tremendously powerful instruments, able to look deep into space without being limited by the blurring effects of Earth’s atmosphere. But even this is not enough to allow them to see the most distant galaxies, which are so far away that looking at them is like looking back in time to the early stages of the universe.

To look even further out, astronomers take advantage of a phenomenon called gravitational lensing. This happens when an object like a galaxy or a galaxy cluster has so much mass that it bends space-time, acting like a magnifying glass and brightening the extremely distant objects behind it.

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This is how the James Webb Space Telescope was recently able to see thousands of extremely distant objects by looking at a region of space called Pandora’s Cluster, or Abell 2744.

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Bright white sources surrounded by a hazy glow are the galaxies of Pandora’s Cluster, a conglomeration of already-massive clusters of galaxies coming together to form a megacluster.
Astronomers estimate 50,000 sources of near-infrared light are represented in this image from NASA’s James Webb Space Telescope. Their light has traveled through varying distances to reach the telescope’s detectors, representing the vastness of space in a single image. A foreground star in our own galaxy, to the right of the image center, displays Webb’s distinctive diffraction spikes. Bright white sources surrounded by a hazy glow are the galaxies of Pandora’s Cluster, a conglomeration of already-massive clusters of galaxies coming together to form a megacluster. SCIENCE: NASA, ESA, CSA, Ivo Labbe (Swinburne), Rachel Bezanson (University of Pittsburgh) IMAGE PROCESSING: Alyssa Pagan (STScI)

Three galaxy clusters in the center of the image form a megacluster, which has so much mass it allows astronomers to see areas of space never observed before.

“When the images of Pandora’s Cluster first came in from Webb, we were honestly a little star-struck,” said one of the researchers, Rachel Bezanson, in a statement. “There was so much detail in the foreground cluster and so many distant lensed galaxies, I found myself getting lost in the image. Webb exceeded our expectations.”

If you look closely at the image, you’ll see that many of the galaxies appear to be stretched out or elongated. That’s because of the lensing effect, as the gravity of the megacluster warps the light coming from them. But even with this distortion, astronomers can learn a lot about these galaxies from images like this one.

The data for this image was collected using Webb’s NIRCam instrument and combines around 30 hours of observing time. Next, the researchers will choose particular galaxies of interest and observe these in more detail using Webb’s NIRSpec instrument to see their compositions, adding more information to this rich tapestry.

“Pandora’s Cluster, as imaged by Webb, shows us a stronger, wider, deeper, better lens than we have ever seen before,” said another of the researchers, Ivo Labbe. “My first reaction to the image was that it was so beautiful, it looked like a galaxy formation simulation. We had to remind ourselves that this was real data, and we are working in a new era of astronomy now.”

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