Supernova "Encore" within Galaxy MRG-M0138

In 2016, the Hubble Space Telescope captured a supernova named Requiem in the distant galaxy MRG-M0138. Seven years later, in 2023, during the Webb Telescope’s observations of the same galaxy, a second supernova named Encore was discovered — marking the first time two gravitationally lensed supernovae have been found in the same galaxy. Gravitational lensing occurs when an object, such as a galaxy cluster, has such intense gravity that it warps surrounding space and time. Light follows that curve instead of traveling in a straight line, distorting and brightening the objects behind it. Not only does gravitational lensing warp and magnify distant galaxies, but it can also reveal multiple images of the same object. Hubble’s 2016 image displayed three separate instances of supernova Requiem, while Webb’s newer image shows two instances of Encore (visible as two faint dots in the lower arc). By measuring the differences in the times when these supernova images appear, astronomers can determine how fast the universe is expanding. An alternative view focusing on the area containing the supernovae is available.