Figure 14-22 Dimmer Distant Supernova (a) These Hubble Space Telescope images show the galaxy in which the Type Ia supernova SN 1997ff occurred. This supernova, more than 10 billion light-years away, was dimmer than expected, indicating that the distance to it is greater than the distance it would have if the universe had been continually slowing down since the Big Bang. This supports the notion that an outward (cosmological) force is acting over vast distances in the universe. The arrow on the left inset shows the galaxy in which the supernova was discovered. The bright spot on the right inset shows the supernova by subtracting the constant light emitted by all the other nearby objects. (b) The distances and brightnesses of many very distant supernovae are plotted on this diagram. The locations of the most distant supernovae in the upper region strongly indicate that the universe has been accelerating outward for the past 6 billion years.