In Greek mythology, Pandora’s curiosity leads to opening a container that releases all the evils and hardships that now exist in the world.
Let’s hope the James Webb Space Telescope (JWST) didn’t do just that when it zoomed into a region of space called “Pandora’s Cluster” using a phenomenon predicted by Einstein in 1915. The new JWST image reveals previously hidden details from the region and the merging of three already massive clusters to create an even larger “megacluster” of galaxies.
The nickname for this region, officially known as Abell 2744, of the Pandora cluster comes from observing a number of different structures within it. So far, however, only the central core of this region of space has been studied by the Hubble Space Telescope, meaning many mysteries remained undiscovered as the JWST turned its powerful infrared instruments on the area.
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The JWST team viewed the Pandora cluster with the powerful telescope near infrared camera (opens in new tab) (NIRCam) and the Near infrared spectrograph (opens in new tab) (NIRSpec) instruments as part of the pre-reionization epoch Ultradeep NIRSpec and NIRCam observations (DISCOVER (opens in new tab)) program. The resulting deep-field image takes four JWST “snapshots” and stitches them together. This resulted in a panoramic image with a breathtaking 50,000 infrared light sources.
This resulted in a deep-field image of the Pandora cluster, some 3.5 billion light-years away, that achieved an impressive balance of breadth and depth that could revolutionize the study of galactic evolution.
A bright star in the foreground of the Milky Way is highlighted in the image with prominent diffraction peaks generated by the JWST. Around him are bright sources of white light surrounded by a hazy glow; These are the much more distant galaxies of the Pandora cluster.
Although man-made technology is essential for observing this cluster of clusters, astronomers also relied on a natural phenomenon first revealed by Albert Einstein in his 1915 work, the theory of gravitation, known as general relativity.
Einstein provides the key to opening Pandora’s cluster
General relativity predicts that mass objects will affect and distort the fabric of space. This is equivalent to placing objects on a stretched sheet of rubber and making dents in the sheet. Just as bullets of increasing mass would create larger, more extreme dents in this layer, so cosmic objects of enormous mass create large curvatures in the fabric of space. This curvature can be so extreme that the light’s path as it passes through is also curved.
That is, when light from a background object passes an extremely massive body in the foreground on its way to Earth, it can appear as if the background object has shifted its position in the sky. This gravitational lensing effect can also have other consequences. Sometimes the foreground bulk object or “lensing object” can actually help to amplify the light from background objects.
This gain helps the already powerful JWST see the light from distant, and therefore early, galaxies that are too faint to observe without lenses. The lens can also distort background objects, stretching them like cosmic toffee as its light takes different paths around the lens object with different transit times. This distortion helps astronomers determine which galaxies are in the foreground and which are in the background.
An example of this can be seen in the new JWST image of the sky section including the Pandora cluster. Hundreds of distant, strongly lensed galaxies appear as arcs of light in the lower right of the image. These galaxies have never been seen before, not even by Hubble.
The image was created when NIRCam captured the Pandora cluster with exposures lasting 4 to 6 hours and a total of 30 hours of observation time. These observations will now be followed by an analysis of the region using NIRSpec, which will provide detailed measurements of the distances within the cluster and details about the composition of the galaxies that make it up.
This new data, due to be released this summer, should provide entirely new insights into how galaxies in the early Universe came together and how they evolved into the cosmos we see around us today.
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