Imagine drawing two dots on a balloon spread apart by an inch. When you inflate the balloon, what happens to the distance between the dots? It increases. A similar phenomenon occurs between us and very distant galaxies because the universe is expanding just like the balloon that is inflating. This expansion increases the distance between us and galaxies at the edge of existence. When we look out towards the depths of the universe, we are actually peering back in time, as the speed of light is finite. Once the light from very distant galaxies reaches us we actually see the galaxy as it looked millions if not billions of years ago. Thus, it is crucial to understand remote galaxies because we can gain insight into how galaxies form and evolve by comparing distant galaxies to younger, nearby galaxies. In order to study distant galaxies, astronomers conduct deep field imaging surveys, where they point powerful space telescopes at small but deep patches of sky for long amounts of time to collect as much light as they can. From these surveys they typically detect thousands of galaxies near the horizon of the observable universe.

One such deep field observed by the James Webb Space Telescope, the UNCOVER survey, targets a conglomerate of gravitationally bound galaxies called Abell-2744, nicknamed Pandora’s Cluster. Pandora’s Cluster is known as a gravitational lensing cluster, as it is so massive it bends and distorts light from objects that appear behind it, as seen in Figure 1.

Bending of light from a galaxy collected by a space telescope

Depicted is the bending of light (white lines) from a very distant galaxy around a galaxy cluster and collected by a space telescope, such as the James Webb Space Telescope. This concept stems from Einstein's theory of general relativity, which describes how massive objects bend light. (Credit: NASA/James Webb Space Telescope)

 The UNCOVER survey has detected about 60,000 galaxies, and Dr. John Weaver, a postdoc at UMass Amherst, and his international team of collaborators worked on creating a catalog of the survey for the community. This involved measuring basic properties, like color and distance, for each galaxy. The team's grueling yet heroic work enables an immense amount of future research, as astronomers can now use the public catalog of the 60,000 galaxies for their own research. John reflects, “The paper was not just sharing the catalog… but sharing the insights, the tests, and how we solved things, and in my mind that’s half the story. And I’ve heard back from other teams that have used our methods, which is super exciting”. This shows the collaborative nature that is astronomy and how people from around the world come together to help the astronomy community as a whole.


Pictured is John Weaver (UMass Amherst) presenting his research on cataloging the UNCOVER survey at the 243rd meeting of the American Astronomical Society in January 2024, which was held in New Orleans.

So far, the UNCOVER survey has made some astounding detections revealing roughly a dozen of the most distant galaxies ever measured, as well as the remarkable discovery of an active supermassive black hole lensed and magnified such that it appears in three different locations – and at three unique points in time. The UNCOVER survey field is also known to include the most distant black hole with detected x-ray emission, at an astonishing 26 billion light years away – meaning we see it as it appeared only a mere 700 million years after the Big Bang.

By observing these extremely distant galaxies in their infancy, John hopes to learn more about the origins of massive galaxies and how galaxies become so humongous over cosmic time. UNCOVER also obtained spectra from JWST for 500 of the most interesting objects in the survey. A spectrum is collected by splitting the light we observe from a galaxy through a prism into its different colors, allowing astronomers to pick out certain molecules present in the galaxy and provides clues as to the composition and dynamics of the galaxy. Currently, John and collaborators are in the process of processing and analyzing the spectra and they plan to release their findings soon. In the meantime, we can only ponder what other cosmic secrets will be UNCOVERed next.

Open access to the full text of the original paper is available

About the Author:

Moiz Khalil is a senior undergraduate studying astronomy at UMass Amherst. He currently studies the atmospheres and colors of brown dwarfs and wants to pursue a career in science communication. Outside of science, he enjoys listening to music and reading novels.