Gravitational lensing and international teamwork unveils 44 unknown stars
6 Jan 2025
Physicists from across the world studying a distant galaxy in a multinational project have discovered more than 40 previously undetected stars.
Their work outlined in Nature Astronomy, reveals the remote stars’ behaviour 8 billion years ago, during the Universe’s so-called middle age or ‘cosmic noon’.
Of the more than 45 international partners participating, the British contingent included Durham University’s Centre for Extragalactic Astronomy and the Jodrell Bank Centre for Astrophysics, Manchester University. The research was led by Japan’s Centre for Frontier Science at Chiba University.
The collaborators used observations from the James Webb Space Telescope (JWST) to focus on the Dragon Arc galaxy, situated behind Abell 370 cluster of galaxies.
To enhance their work, the scientists employed the technique of gravitational lensing. This employs a foreground galaxy cluster such as Abell 370 to bend light from a more distant object such as the Dragon Arc and magnifies it, allowing an opportunity to study the more distant object.
Combining the technique with high-resolution images from the JWST over a year, the research teams identified 44 previously unknown stars.
Durham’s Dr David Lagattuta said: “When the team made this discovery, we knew that, given the size of the dots seen in the JWST images, the most logical explanation was that these were individual stars, seen for the first time, which is a hugely exciting discovery.
“We know these are stars that have not been seen before by comparing them to previous image of the Dragon Arc which do not show these bright dots.”
Many of the stars identified through this study are ‘red supergiants’, previously difficult to identify when situated outside the Milky Way because their layer of cosmic ‘dust’ had rendered them almost invisible to most telescopes but not to the JWST.
Professor Mathilde Jauzac from the Centre for Extragalactic Astronomy and the Institute for Computational Cosmology at Durham said: “This is the first time, that we are aware of, that so many stars have been discovered in one cluster. This finding enables us to see what the galaxy is made of in ways not possible before.”
She added that star behaviour and development started to change around the cosmic noon; thus the new study provides an insight into that point in time
The researchers plan to develop their studies of the Dragon’s Arc, to differentiate between stellar populations being magnified by the cluster, so providing extra information about how stars formed and existed in that era of their development.
Photo: Greg Rakozy
