Transcript: We view the Milky Way from a position within its enormous disk. The Milky Way disk is thirty thousand parsecs across, roughly four hundred parsecs thick, and it’s packed with young stars, gas clouds, obscuring dust, open clusters, and active star formation regions. The disk is imbedded within a spherical halo composed of galactic globular clusters and individual halo stars. The halo looks diffuse, but it actually contains most of the mass of the Milky Way galaxy. We’re located about eight thousand five hundred parsecs from the galactic center, and astronomers in talking about galactic distances use a different unit, the kiloparsec or a thousand parsecs. In these terms the galactic center is eight and a half kiloparsecs away, and the Milky Way is thirty kiloparsecs across. To give a sense of the scale of the Milky Way, if the galaxy were the United States, the stars would be individual microscopic specs separated by about a hundred yards each.