Q: What is the shift in wavelength (away from the center) of the line created by each star? shift = about 0.2 nm Q: What is the orbital speed of each star? We use the Doppler formula to calculate the radial velocity of each star: shift radial velocity = --------------- * (speed of light) rest wavelength 0.2 nm = ----------- * 3 x 10^(8) m/s 448.1 nm = 133,000 m/s