The Milky Way galaxy rotates once in 200 million years, and our sun is located about 30,000 light years from the galactic center. As a result, the Earth is moving through space relative to the other galaxies. What is the observed Doppler shift in Å of the hydrogen line of 6563 Å for light coming from other galaxies? Consider two cases:
a. The line of observation is in the direction of the Earth's motion;
b. The line of observation is perpendicular to the direction of the Earth's motion.
Ignore other causes of observed Doppler effects.