Free Astronomy Magazine May-June 2023

33 MAY-JUNE 2023 ASTRO PUBLISHING scope. By combining Webb’s powerful infrared instruments with a broad mosaic view of the re- gion’s multiple areas of lensing, astronomers aimed to achieve a bal- ance of breadth and depth that will open up a new frontier in the study of cosmology and galaxy evolution. “The ancient myth of Pandora is about human curiosity and discoveries that delineate the past from the future, which I think is a fitting connec- tion to the new realms of the universe Webb is opening up, including this deep-field image of Pandora’s Cluster,” said astronomer Rachel Bezanson of the Univer- sity of Pittsburgh in Penn- sylvania, co-principal investigator on the Ultra- deep NIRSpec and NIR- Cam ObserVations before the Epoch of Reionization (UNCOVER) program to study the region. “When the images of Pandora’s Cluster first came in from Webb, we were honestly a little star struck,” said Bezanson. “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 expecta- tions.” The new view of Pandora’s Cluster stitches four Webb snapshots together into one panoramic image, displaying roughly 50,000 sources of near-infrared light. In addition to magnification, gravi- tational lensing distorts the appear- ance of distant galaxies, so they look very different than those in the fore- ground. The galaxy cluster “lens” is so massive that it warps the fabric of space itself, enough for light from data, and we are working in a new era of astron- omy now.” The UN- COVER team used Webb’s Near-Infrared Camera (NIRCam) to capture the cluster with exposures lasting 4-6 hours, for a total of about 30 hours of observing time. The next step is to meticulously go through the imaging data and select galaxies for follow-up observation with the Near-Infrared Spectrograph (NIRSpec), which will provide precise distance measurements, along with other detailed information about the lensed galaxies’ composi- tions, providing new in- sights into the early era of galaxy assembly and evolution. The UNCOVER team expects to make these NIRSpec observa- tions in the summer of 2023. In the meantime, all of the NIRCam photometric data has been publicly released so that other astronomers can become familiar with it and plan their own scientific studies with Webb’s rich datasets. “We are com- mitted to helping the astronomy community make the best use of the fantastic resource we have in Webb,” said UNCOVER co-investiga- tor Gabriel Brammer of the Niels Bohr Institute’s Cosmic Dawn Center at the University of Copenhagen. “This is just the beginning of all the amazing Webb science to come.” The imaging mosaics and catalog of sources on Pandora’s Cluster (Abell 2744) provided by the UNCOVER team combine publicly available Hubble data with Webb photometry from three early observation pro- grams: JWST-GO-2561, JWST-DD- ERS-1324, and JWST-DD-2756. T his video tours Pandora’s Cluster (Abell 2744), a region where multiple clusters of galaxies are in the process of merging 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. The concentration of mass in Pandora’s Cluster is so great that the fabric of spacetime is warped by gravity, creating an effect that makes the region of special interest to astronomers: a natural, super-magnifying glass called a “gravitational lens” that they can use to see very distant sources of light beyond the cluster that would otherwise be undetectable, even to Webb. [Video: STScI, Danielle Kirshen- blat. Music: PremiumBeat Music, Klaus Hergersheimer. Science: Ivo Labbe (Swinburne), Rachel Bezanson (University of Pitts- burgh). Image processing: STScI, Alyssa Pagan] distant galaxies that passes through that warped space to also take on a warped appearance. Astronomer Ivo Labbe of the Swin- burne University of Technology in Melbourne, Australia, co-principal investigator on the UNCOVER pro- gram, said that in the lensing core to the lower right in the Webb image, which has never been imaged by Hubble, Webb revealed hundreds of distant lensed galaxies that appear like faint arced lines in the image. Zooming in on the region reveals more and more of them. “Pandora’s Cluster, as imaged by Webb, shows us a stronger, wider, deeper, better lens than we have ever seen be- fore,” Labbe said. “My first reaction to the image was that it was so beautiful, it looked like a galaxy for- mation simulation. We had to re- mind ourselves that this was real !