The main image features a huge elliptical galaxy surrounded by a cluster of numerous smaller, comparable galaxies, as well as stars and galaxies in the background. A backdrop galaxy's three lensed images are displayed in three smaller pull-outs in close-up..
Credits: ESA/Webb, NASA & CSA, P. Kelly
February 28, 2023
NASA/ESA/CSA James Webb Space Telescope has captured an astonishing view of a supernova-hosting galaxy with the help of colossal gravitational lensing. Gravitational lensing occurs when a massive celestial body bends the path of light, almost like a vast lens. In this case, the lens is the galaxy cluster RX J2129, located 3.2 billion light-years from Earth in the constellation Aquarius.
Astronomers discovered the supernova using observations from NASA/ESA Hubble Space Telescope, and it is suspected to be a very distant Type Ia supernova. These supernovae are helpful to astronomers as they always produce a consistent luminosity, making them useful for measuring astronomical distances.
Using observations from the NASA/ESA Hubble Space Telescope, astronomers discovered the supernova in the triply-lensed background galaxy and suspected that they had found a very distant Type Ia supernova. Type Ia supernovae always produce a fairly consistent luminosity, which makes them helpful to astronomers as their distance from Earth is proportional to how dim they appear in the night sky. Objects with known brightness can be used as 'standard candles' to measure astronomical distances.
The uniform luminosity of a Type Ia supernova could also allow astronomers to understand how strongly the galaxy cluster RX J2129 is magnifying background objects and therefore how massive the galaxy cluster is. Gravitational lenses can cause distant objects to appear much brighter than they would otherwise, and if the gravitational lens magnifies something with a known brightness, such as a Type Ia supernova, then astronomers can use this to measure the ‘prescription’ of the gravitational lens.
The gravitational lens created three lensed images of the background galaxy, each of different size, position, and age. The mass distribution in the galaxy cluster caused the light rays emitted by the supernova to bend in different amounts, resulting in separate images. The oldest image of the galaxy contains the visible supernova, while the next two images show the galaxy as it appeared 320 and 1000 days later, respectively, after the supernova had already faded from view. The transient is named AT 2022riv.
Webb's Near-InfraRed Camera was used to capture the observation and measure the brightness of the lensed supernova. NIRSpec spectroscopy of the supernova was also obtained to compare this distant supernova to Type Ia supernovae in the nearby Universe. This comparison is crucial for verifying astronomers' methods of measuring vast distances.