The radial velocity of a star or other object is measured by:
A) measuring the change in the angular diameter of the object.
B) watching the object move compared with the background stars.
C) measuring the intensity of the light in different regions of the blackbody curve.
D) observing the Doppler shift of spectral lines in the light from the object.

Question

Quizplus · Accepted Answer

The Doppler shift of spectral lines in the light from the object is the most accurate and commonly used method to measure the radial velocity of a star or other object. This method measures the amount of shift in the wavelengths of the absorbed or emitted light and calculates the object's speed of approach or recession relative to the observer.

The Radial Velocity of a Star or Other Object Is