Gravitational Lensing Reveals an Ancient Supernova Through Time

The NASA/ESA/CSA James Webb Space Telescope has captured an incredible shot of the massive galaxy cluster RX J2129, located around 3.2 billion light-years away in the constellation Aquarius. Through gravitational lensing, astronomers have been able to get a closer look at a supernova-hosting galaxy that lies behind the lens.

Gravitational lensing is a phenomenon where a large celestial object exerts a force on spacetime, resulting in the bending of light rays that pass near or through it. It is likened to a giant lens.^[0] In this case, the lens is the galaxy cluster RX J2129, which is so massive that its gravity actually distorts the shape of spacetime, creating a curve that bends light around the cluster.^[1]

The galaxy that we’re seeing mirrored through time is a supernova-hosting galaxy known as AT 2022riv.^[2] Thanks to gravitational lensing caused by a galaxy cluster known as RX J2129, this galaxy, which is situated far away from ours, is visible. Scientists harnessed the potent gravity of a galaxy cluster to delve further into the cosmos, allowing them to observe the distant cosmic mirage.

The Webb shot features a special galaxy cluster – known as RX J2129 – and three different images of the same supernova-hosting galaxy. The galaxy appears not only three times, but at different points in time.^[3] In the initial sight, the supernova was visible, yet it has become less evident in the subsequent views. By viewing the galaxy in three different images, astronomers are able to gauge the decrease in brightness and the alterations in form of the supernova over the course of time.^[4]

The supernova featured in the new image was first discovered using the Hubble Space Telescope, and it was identified as a Type Ia supernova. Type Ia supernovae always produce a fairly consistent luminosity, which makes them particularly helpful to astronomers as they can be used as ‘standard candles' to measure astronomical distances.^[5]

NIRSpec spectroscopy of the supernova was also obtained as part of the same programme, enabling a comparison to Type Ia supernovae in the nearby Universe. To ensure that astronomers' long-established technique for gauging great distances remains accurate, this is a crucial step.^[5]

The James Webb Space Telescope continues to beam back breathtaking images of the cosmos.^[6]

0. “Webb telescope sees bizarre galaxy cluster triplets mid-supernova” Mashable, 2 Mar. 2023, https://mashable.com/article/james-webb-space-telescope-galaxy-cluster-supernova

1. “JWST Sees the Same Supernova Three Times in an Epic Gravitational Lens” Universe Today, 2 Mar. 2023, https://www.universetoday.com/160353/jwst-sees-the-same-supernova-three-times-in-an-epic-gravitational-lens/

2. “James Webb photographs cosmic mirage of a galaxy far, far away” BGR, 2 Mar. 2023, https://bgr.com/science/webb-snaps-cosmic-mirage-of-a-galaxy-far-far-away/

3. “Wild Webb Telescope Image Shows the Same Galaxy 3 Times” CNET, 2 Mar. 2023, https://www.cnet.com/science/space/wild-webb-telescope-image-shows-the-same-galaxy-3-times

4. “Webb Telescope Captures Epic Cosmic Mirage of a Distant Galaxy” Inverse, 1 Mar. 2023, https://www.inverse.com/science/how-astronomers-will-measure-the-curves-of-a-gravitational-lens

5. “ESA – Seeing triple” European Space Agency, 28 Feb. 2023, https://www.esa.int/ESA_Multimedia/Images/2023/02/Seeing_triple

6. “Webb telescope observes massive galaxy cluster 3.2 billion light-years from Earth” Devdiscourse, 28 Feb. 2023, https://www.devdiscourse.com/article/science-environment/2364308-webb-telescope-observes-massive-galaxy-cluster-32-billion-light-years-from-earth