Astronomers call the motion of a star across the sky (perpendicular to our line of sight) its
A) radial velocity
B) Doppler shift
C) light travel time
D) proper motion
E) spectral type

Question

Quizplus · Accepted Answer

Proper motion refers to the motion of a star across the sky which is perpendicular to our line of sight. Radial velocity refers to the motion of a star towards or away from us along our line of sight. Doppler shift refers to the change in wavelength of light due to motion, which can be used to determine radial velocity. Light travel time refers to the time it takes for light to travel from a star to Earth. Spectral type refers to the classification of a star based on its spectrum.

Astronomers Call the Motion of a Star Across the Sky