What is the star’s radial velocity with respect to Earth?
jgoulden Teacher Graduate School eNotes Editor The Ha line as measured from a source at rest has a wavelength of 656.3 nm. Your star’s Ha line is at a slightly shorter wavelength, so that star is moving towards the Earth. To find the radial velocity (which, given how close the wavelengths are, we expect to be fairly low), we use the non-relativistic Doppler shift: L_measured / L_rest = 1 + v / c 655.3 / 656.3 = 1 + v / c v = -.00152 c The star is approaching at about .15% of the speed of light, or about 4.57 x 10^5 m/s. Sources: http://en.wikipedia.org/wiki/Red_shift Rate answer: $(‘#aScore-126539’).
