Nicholas Barnard PHY117: Crab Nebula 2/27/02
1. My result for the age of the Crab Nebula of 1076 years is in reasonable agreement with the year 1054 from the imperial observations of Chinese astronomers in 1054. Our calculation has an error rate of 2.04% from the expected value. This is a reasonable error rate because of the size of the photographs being compared. For instance if the photographs were bigger the precision of the measurements would increase because the measured distances would be larger, and the percentage error rate of each individual measurement would be less because of greater accuracy.
2. The other answers that I have derived are in reasonable agreement with the answers in the reprint. The error rates for several of the intermediate figures are well below 4%.
3. In looking at the two photographs it is not possible to tell whether the nebula was brighter in 1942 or 1976, because each of the photographs was taking with different equipment. The 1942 photograph was taken on a 100-inch telescope with a two and a half hour exposure. The 1976 photograph was taken on a 158" reflector telescope with a twenty-minute exposure. In addition items view through reflector telescopes generally appear darker than an item view in a similar refractor telescope. To further muddle the accuracy of comparing brightness in the photographs is the fact that the film stocks on which the photographic negatives is not known to us, therefore we cannot make adjustments to compensate for the photosensitivity of the film stock.
Nicholas Barnard PHY117: Pulsars 2/27/02
1. The "maximum possible size" of a pulsar can be no larger than the distance light travels during a "large change" in the output of the pulsar.
2. High frequency radio waves are slowed down more in space. All radio waves are slowed down because of free electrons in space.