The Tully-Fisher method for measuring the distance to galaxies relies on the observed relationship between the luminosity of a spiral galaxy and
A) its rotational velocity (as determined from the width of the 21-cm line)
B) its number of high-energy sources (as determined from the total gamma-ray emission)
C) the size of its supernova remnants (as determined from radio maps)
D) the number of globular clusters (as determined from high-resolution images)
E) the number of companion galaxies found directly around it
Section 26.5: The Expanding Universe

Question

Quizplus · Accepted Answer

The Tully-Fisher method relates the rotation speed (measured from the width of the 21-cm line) of a spiral galaxy to its luminosity, allowing astronomers to estimate the distance to the galaxy based on its observed brightness.

The Tully-Fisher Method for Measuring the Distance to Galaxies Relies