Light from the distant supernova-hosting galaxy was gravitationally lensed by the foreground galaxy cluster RX J2129.6+0005 (RX J2129 for short).
This Webb image shows the massive galaxy cluster RX J2129.6+0005; due to gravitational lensing, this observation contains three different images of a distant galaxy that hosted the Type Ia supernova event AT 2022riv. Image credit: NASA / ESA / CSA / Webb / P. Kelly.
Galaxy clusters contain thousands of galaxies of all ages, shapes and sizes.
Typically, they have a mass of about one million billion times the mass of the Sun.
Albert Einstein predicted in his theory of general relativity that massive objects will deform the fabric of space itself.
When light passes one of these objects, such as a massive galaxy cluster, its path is changed slightly.
Called gravitational lensing, this effect is only visible in rare cases and only world’s best telescopes can observe the related phenomena.
“Gravitational lensing occurs when a massive celestial body causes a sufficient curvature of spacetime to bend the path of light traveling past or through it, almost like a vast lens,” Webb astronomers said.
“In this case, the lens is the galaxy cluster RX J2129, located around 3.2 billion light-years from Earth in the constellation of Aquarius.”
“Gravitational lensing can cause background objects to appear strangely distorted, as can be seen by the concentric arcs of light in the upper right of the Webb image.”
The astronomers discovered a supernova called AT 2022riv in the triply-lensed background galaxy using observations from the NASA/ESA Hubble Space Telescope, and they suspected that they had found a very distant Type Ia supernova.
Type Ia supernovae always produce a fairly consistent luminosity — at the same distance, one looks as bright as any other — which makes them particularly 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 almost 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.
“As well as distorting the images of background objects, gravitational lenses can cause distant objects to appear much brighter than they would otherwise,” the astronomers said.
“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.”
This observation was captured by Webb’s Near-InfraRed Camera to measure the brightness of AT 2022riv.
As part of the same program, spectra of the lensed supernova were obtained using Webb’s Near Infrared Spectrograph.
They will allow comparison of this distant supernova to Type Ia supernovae in the nearby Universe.
“This is an important way to verify that one of our tried-and-tested methods of measuring vast distances works as expected,” the researchers said.
Source : Breaking Science News