Milky Way galaxy spiral arms, labelled animation. The arms of our home galaxy are marked in green and named: the Perseus arm, the Local arm fragment (including our Sun, labelled in red), the Norma arm, the Sagittarius arm, and the Scutum-Crux arm. There are four major arms, as the part marked Local is an arm fragment (also called Orion-Cygnus). It is thought that the Milky Way, which is around 200, 000 light years across, contains 100 to 400 billion stars. For this animation without labels, see clip K007/8868 |