Webb telescope spots second gravitationally lensed supernova in distant galaxy

In 2019, the NASA/ESA Hubble Space Telescope saw a supernova, nicknamed Supernova Requiem, in a distant galaxy named MRG-M0138. Now seven years later, the James Webb Space Telescope has detected another gravitationally lensed supernova within the same galaxy, marking the first-ever instance of two gravitationally lensed supernovae in a single galactic host.

Gravitational lensing occurs when the immense gravitational pull of a foreground galaxy cluster, in this case, MACS J0138.0-2155, distorts and magnifies the light from a more distant object, such as the galaxy MRG-M0138. The result is a warped appearance of the distant galaxy and the formation of multiple images, in this instance, five distinct images of MRG-M0138.

The second supernova, named Supernova Encore, was uncovered using Webb's NIRCam (Near-Infrared Camera) instrument. It has been categorised as a standard candle or type Ia supernova.

Encore and Requiem are by far the most distant pair of standard-candle supernova siblings ever discovered, according to the researchers.

"Now we have found a second gravitationally lensed supernova within the same galaxy as Requiem, which we call Supernova Encore. Encore was discovered serendipitously, and we are now actively following the ongoing supernova with a time-critical director’s discretionary program. Using these Webb images, we will measure and confirm the Hubble constant based on this multiply-imaged supernova. Encore is confirmed to be a standard candle or type Ia supernova, making Encore and Requiem by far the most distant pair of standard-candle supernova ‘siblings’ ever discovered," said Justin Pierel, NASA Einstein Fellow at the Space Telescope Science Institute and Andrew Newman, staff astronomer at the Observatories of the Carnegie Institution for Science.

Supernova 2: Galactic Boogaloo In 2016, @NASAHubble saw a supernova named Requiem in a distant galaxy. Now Webb has found a second supernova named Encore — marking the first time two gravitationally lensed supernovae have been found in the same galaxy: https://t.co/L3dZjYbulW pic.twitter.com/jFXKR3I2aN

— NASA Webb Telescope (@NASAWebb) December 21, 2023