The radial velocity curve of a star in a binary star system is a plot against time of the
A) speed of the star in a direction perpendicular to the line of sight to the star.
B) position of the star in celestial coordinates.
C) variation of Doppler shift of the star's spectral lines and hence of its speed toward or away from Earth.
D) temperature of the star as determined from the movement of the peak wavelength of its spectrum.

Question

Quizplus · Accepted Answer

The radial velocity curve of a star in a binary star system shows the variation of the Doppler shift of the star's spectral lines, which indicates its speed toward or away from Earth. This is because the Doppler effect causes the spectral lines to shift in wavelength depending on the motion of the star relative to the observer.

The Radial Velocity Curve of a Star in a Binary