Halliday, Resnick & Walker — Relativity: Problem 10

10 Figure 37-16 is a graph of intensity versus wavelength for light reaching Earth from galaxy NGC 7319, which is about \(3 \times 10^8\) light-years away. The most intense light is emitted by the oxygen in NGC 7319. In a laboratory that emission is at wavelength \(\lambda = 513 \text{ nm}\), but in the light from NGC 7319 it has been shifted to \(525 \text{ nm}\) due to the Doppler effect (all the emissions from NGC 7319 have been shifted). (a) What is the radial speed of NGC 7319 relative to Earth? (b) Is the relative motion toward or away from our planet? (c) Is the wavelength shift a red shift or a blue shift?