Astronomers have been arguing over just how many spiral arms our Galaxy exhibits. Is the Milky Way a four or two-armed spiral galaxy? Astronomers had often assumed the Milky Way was potentially a four-armed spiral galaxy, but comparatively recent observations from NASA’s Spitzer telescope implied the Galaxy had two spiral arms.  In 2013, astronomers mapped star forming regions and argued they had found the two … Continue reading More Evidence that the Milky Way has Four Spiral Arms