These HST images show five supernovae and their host galaxies. The righthand column of images shows the supernovae. The lefthand side shows the host galaxies before or after the stars exploded. The supernovae exploded between 3.5 and 10 billion years ago. Scientists used these supernovae to measure how dark energy has affected the universe's expansion rate over time.
NASA/ESA/R. Riess (STScI)