In November 2023, the James Webb Space Telescope observed the giant galaxy cluster MACS J0138.0-2155. Gravitational lensing causes a distant galaxy called MRG-M0138 to appear distorted. In addition to the distortion and expansion of distant galaxies, the gravitational lensing effect caused by MACS J0138 produces his five different images of MRG-M0138. In 2019, astronomers announced a surprising discovery. MRG-M0138 experienced an internal stellar explosion, or supernova, as seen in his 2016 image from NASA’s Hubble Space Telescope.

Another team of astronomers examined Web 2023 images and found that a second supernova erupted in the same galaxy seven years later. Justin Pirrell (NASA scientist) and Andrew Newman (staff astronomer at Carnegie Scientific Observatory) tell us more about this discovery. “When a supernova explodes behind a gravitational lens, its light follows many different paths to reach Earth. You can compare it to a train.”

Each train follows a different route, with different travel times and terrain, so the trains do not arrive at their destination at the same time. ” By measuring differences in the timing of supernova images, we can measure the history of the universe’s expansion rate, known as the Hubble constant, a major problem in cosmology today. “The problem is that these repeatedly photographed supernovae are extremely rare, with fewer than a dozen ever discovered.

Among this small club, MRG-M0138’s 2016 supernova called Requiem stood out for several reasons. First, it was 10 billion light years away. Second, the supernova was probably the same type (Ia) used as a “standard candle” for measuring distances in the universe. ”

We discovered a second gravitational lensing supernova, Supernova Encore, in the same galaxy as Requiem. Encore was discovered by chance, and we are currently actively monitoring this supernova. » “Using Webb images, we measure and confirm the Hubble constant based on these multiple images of supernovae. Encore is confirmed to be a standard candle or type Ia supernova.” “Supernovae are generally Although unpredictable, in this case we know when and where we will see the final appearances of Requiem and Encore. Infrared observations around 2035 will provide precise new measurements of the Hubble constant.”

source: https://ui.adsabs.harvard.edu/abs/2020AAS…23522806J/abstract