How do we measure the mass of a spiral galaxy?
How do we measure the mass of a spiral galaxy? Astronomers can calculate the masses of some spiral galaxies by determining their rotation speed by measuring the Doppler shift of various spectral lines versus distance from the galactic center. The mass within any given radius then follows directly from Newton's laws. How do astronomers observe the spiral structure of the Milky Way? Astronomers using data from NASA's Wide-field Infrared Survey Explorer, or WISE, are helping to trace the shape of our Milky Way galaxy's spiral arms. This illustration shows where WISE data revealed clusters of young stars shrouded in dust,...