CoachThe Galactic disc is the flattened component of the Galaxy, made of stars, gas and dust in nearly circular orbits about its centre; its density falls off roughly exponentially with height above its mid-plane and with distance from its centre, over a scale height and a scale length. The thick disc is a second, older disc component of larger scale height and smaller mass. The Galactic bulge is the central concentration of stars that swells out of the disc. The stellar halo is the sparse, roughly spheroidal component of old stars and globular clusters that surrounds the disc and the bulge.
