What is the best way to determine a galaxy's redshift?
A)Take a spectrum of the galaxy, and measure the difference in wavelength of spectral lines from the wavelengths of those same lines as measured in the laboratory.
B)Measure the magnitude of the galaxy, estimate its distance, and calculate its redshift using Hubble's Law.
C)Find the color of the galaxy, and estimate its distance based on how red the galaxy is.
D)Find the galaxy's apparent distance, and look up the redshift based on Hubble's Law.

Question

Quizplus · Accepted Answer

Taking a spectrum of the galaxy allows for the direct measurement of the difference in wavelength of spectral lines, which can be used to determine the galaxy's redshift. This is a more precise method than estimating distance and using Hubble's Law, which is subject to uncertainties and errors. Color and apparent distance are also not reliable indicators of redshift.

What Is the Best Way to Determine a Galaxy's Redshift