Leiden University astronomers capture new details in Pandora’s Cluster
Astronomers have captured a new deep field of Pandora’s Cluster (Abell 2744) with the James Webb Space Telescope. The images show never-before-seen details. The results are described in four scientific papers. Leiden astronomers Marijn Franx and Mariska Kriek collaborated on the study. ‘This opens a new perspective on the evolution of galaxies.’
The new Webb image shows three clusters of massive galaxies forming a mega-cluster together. The combined mass of the clusters creates a powerful gravitational lens, a natural magnification effect of gravity. This allows astronomers to observe much more distant galaxies in the early universe. Pandora’s Cluster lies in the southern constellation Sculptor, 3.5 billion light years from Earth. The new image of Pandora’s Cluster merges four Webb pictures into one panoramic image and shows roughly 50,000 sources in near-infrared light.
Only Pandora’s central core has previously been studied in detail by the Hubble Space Telescope. By combining Webb’s infrared instruments, with a broad mosaic image of the different lensing regions in the area, the astronomers arrived at this wide and deep field. According to Mariska Kriek, this ‘opened a new window to the study of cosmology and the evolution of galaxies.’
Webb exceeds expectations
‘When the Webb images of Pandora’s Cluster came in, we were a bit overwhelmed,’ says astronomer Rachel Bezanson. She is co-principal investigator of the Webb programme that did this research, named ‘Ultradeep NIRSpec and NIRCam ObserVations before the Epoch of Reionisation’ (UNCOVER). ‘There were so many details in the foreground cluster and so many distant, lensed galaxies, that I got lost in the image. Webb exceeded our expectations.’
Apart from magnification, the gravitational lens distorts the appearance of distant galaxies in a way that they look very different from those in the foreground. The lens effect of the cluster is so strong that it distorts the fabric of space itself. As a result, light from distant galaxies travelling through that distorted space, also looks distorted.