Astronomy

120 hours from JWST

Tuesday, May 27, 2025

Webb's deepest image yet: 120 hours from JWST reveals distant galaxies warped by gravitational lensing around cluster Abell S1063, offering a glimpse into Cosmic Dawn and uncovering potential evidence of the Universe’s earliest stars.

The central focus of the latest James Webb Space Telescope "Picture of the Month," a collaboration between NASA, ESA, and CSA, is the immense galaxy cluster Abell S1063. Located approximately 4.5 billion light-years from Earth in the constellation Grus (the Crane), this enormous collection of galaxies dominates the visual field. Upon closer examination, the dense cluster is surrounded by glowing, warped arcs of light—distant galaxies whose appearance has been altered by gravitational lensing, making them the true target of scientific investigation.

Photo credit: ESA/Webb, NASA & CSA, H. Atek, M. Zamani (ESA/Webb), N. Bartmann (ESA/Webb)

Abell S1063 was previously observed through the Hubble Space Telescope’s Frontier Fields programme. As a powerful gravitational lens, the massive cluster bends the light of galaxies situated behind it. This warping effect, similar to the optical focusing of a glass lens, magnifies and brightens the images of distant galaxies, albeit with some distortion. Hubble's use of this lensing phenomenon aimed to study some of the earliest galaxies in the Universe.

120 hours from JWST: A deep field view of Abell S1063

New observations made with Webb’s Near-Infrared Camera (NIRCam) extend this effort further into the cosmic past. The image reveals a rich tapestry of lensing arcs around Abell S1063, exposing background galaxies across a wide range of distances. Many of these galaxies are extremely faint or previously undetected, revealing new structural and compositional features.

The image represents a deep field, an extended exposure of a specific area of the sky designed to collect the maximum possible light from the faintest and most distant celestial objects. Composed of nine separate exposures across various near-infrared wavelengths and totaling roughly 120 hours of observation time, this image is the most in-depth view that Webb has obtained of a single target to date. The added magnifying effect of the gravitational lens significantly enhances Webb’s ability to detect the earliest galaxies that formed in the young Universe.

The data comes from the GLIMPSE programme (General Large programme for Investigating Distant galaxies with Multi-band Photometry and Spectroscopy, #3293), led by principal investigators H. Atek and J. Chisholm. The programme seeks to explore the Cosmic Dawn era, a period when the Universe was only a few million years old. By studying galaxies unveiled through gravitational lensing, GLIMPSE researchers aim to better understand how the first galaxies emerged. Preliminary analysis of the NIRCam data has already identified candidates for galaxies that may have existed as early as 200 million years after the Big Bang, along with indications of the Universe’s first population of stars.