The question below refers to the diagram above, showing the same spectral feature as measured in a lab, and in four stars. Wavelength increases to the right. The wavelength of this spectral feature is measured to be 600nm in the lab, and 609 in Star A. What is the radial velocity of Star A? Enter the answer in the box below using km/s, but only enter the number.

The question below refers to the diagram above, showing the same spectral feature as measured in a lab, and in four stars. Wavelength increases to the right. The wavelength of this spectral feature is measured to be 600nm in the lab, and 609 in Star A. What is the radial velocity of Star A? Enter the answer in the box below using km/s, but only enter the number.