NASA's Hubble tracked a supernova fading over one year in a galaxy 70 million light-years away

NASA/ESA's Hubble Space Telescope tracked the fading light of supernova SN 2018gv in the barred spiral galaxy NGC 2525, about 70 million light-years away in the constellation Puppis. The supernova was first spotted in mid-January 2018, and Hubble observed it from February 2018 to February 2019, producing a time-lapse released on October 1, 2020, that shows it outshining the galaxy's brightest stars before fading away. It was a Type Ia supernova, which reaches a consistent peak brightness about 5 billion times that of the Sun, so astronomers use such explosions as cosmic tape measures to calculate distances to galaxies. Using those distances, Adam Riess's team had narrowed its measurement of the universe's expansion rate to 1.9% uncertainty by 2020, aiming for 1%. Credit: ESA/Hubble, Digitized Sky Survey, L. Calçada, Nick Risinger (skysurvey.org)