Free Astronomy Magazine January-February 2023

45 JANUARY-FEBRUARY 2023 ASTRO PUBLISHING the fading super- nova’s rapid change of colour, which in- dicates its changing temperature. The bluer the colour, the hotter the super- nova is. The earliest phase captured ap- pears blue. As the su- pernova cooled its light turned redder. This is also the first time astronomers have been able to measure the size of a dying star in the early Universe. They did this by observing the supernova’s bright- ness and rate of cool- ing, both of which depend on the size of the progenitor star. Hubble’s observa- tions show that the red supergiant whose supernova explosion the researchers dis- covered had a radius about 500 times larger than the Sun. An international team of astronomers found this supernova by sifting through the Hubble data archives, looking for transient events. The team also has time planned for the NASA/ESA/CSA James Webb Space Tele- scope to observe even more distant su- pernovae. They hope to contribute to a cat- alogue of very far-off supernovae to help astronomers understand if the stars that existed many billions of years ago are different from those in the nearby Universe. T hrough the phenomenon of gravitational lensing, the NASA/ESA Hubble Space Telescope cap- tured three different moments in the explosion of a very far-off supernova—all in one picture! In this case, the immense gravity of the galaxy cluster Abell 370 acted as a cosmic lens, bending and magnifying the light from the more distant supernova located behind the cluster. The warping also produced multiple images of the explosion over different time periods that all arrived at Hub- ble simultaneously. The top box shows a portion of Abell 370. The box-within-the-box marks the area where the distant supernova was multiply lensed. The bottom image is a magnified version of this area with the light paths marked for the three images of the supernova. The right side of the bottom image shows the distant galaxy in which the supernova exploded. The lines show how the light travelled through the gravitational lens, with some of the light taking longer routes across “valleys” of warped space. The warping produced three images of the explosion over differ- ent time periods that all arrived at Hubble simultaneously. [NASA, ESA, A. Pagan (STScI)] Abell 370, bending and magnifying the light from the more distant su- pernova located behind the cluster. The three paths were of three dif- ferent lengths, so when the light ar- rived at Hubble (on the same day in December 2010), the supernova ap- peared at three different stages of evolution. The Hubble exposure also captured !