The Rotation Curve of the Milky Way Galaxy as Evidence for Dark Matter

Abstract

We present neutral hydrogen observations of the plane of the Milky Way galaxy between 0° < l < 80° galactic longitude on the 20-meter telescope at the Green Bank Observatory. These radio spectroscopic signatures returned the 21-cm line of neutral hydrogen at various offsets due to the Doppler shift. By calculating orbital speeds relative to the galactic center, velocity was plotted against radial distance to map the rotation curve of the Milky Way galaxy. The distribution of luminous matter suggests that orbital velocity should fall off at large distances, but empirical observations show otherwise. An abundance of mass which cannot be detected is responsible for this phenomenon, known as dark matter. Although its nature is not understood, dark matter is easily observed indirectly by galactic rotation curves. Our observations confirm that the velocity of the Milky Way’s disk is fairly constant even at large distances from the center of our galaxy, Sagittarius A*.