A supernova is a violent explosion that occurs at the

Chapter 24, Problem 24.6

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A supernova is a violent explosion that occurs at the death of certain stars. For a few days after the explosion, the intensity of the emitted light can become a billion times greater than that of our own sun. After several years, however, the intensity usually returns to zero. Supernovae are relatively rare events in the universe; only six have been observed in our galaxy within the past 400 years. A supernova that occurred in a neighboring galaxy, approximately 1.66 1021 m away, was recorded in 1987. Figure 24.13 shows a photograph of the sky (a) before and (b) a few hours after the explosion. Astronomers say that viewing an event like the supernova is like looking back in time. Which one of the following statements correctly describes what we see when we view such events? (a) The nearer the event is to the earth, the further back in time we are looking. (b) The farther the event is from the earth, the further back in time we are looking