What change in wavelength would this cause in the Balmer gamma line?

Question

The highest-velocity stars an astronomer might observe have velocities of about 400 km/s. What change in wavelength would this cause in the Balmer gamma line?

Answer 1

Hi. Depends on the radial component of the star's motion. They could shift toward the blue end of the spectrum (unlikely) or towards the red end. The ratio is, of course, 400/300,000.