Question

Describe two substantially different astronomical measurements that are made

possible by the Doppler shift of light. Include a diagram for each.

Answer 1

Astronomers use Doppler shifts to calculate precisely how fast stars and other astronomical objects move toward or away from Earth. For example the spectral lines emitted by hydrogen gas in distant galaxies is often observed to be considerably redshifted. The spectral line emission, normally found at a wavelength of 21 centimeters on Earth, might be observed at 21.1 centimeters instead. This 0.1 centimeter redshift would indicate that the gas is moving away from Earth at over 1,400 kilometers per second (over 880 miles per second).

Doppler effect: = _rest × V_radial/c, where V_radial is the object's speed along the line of sight and c is the speed of ligh