bulging concentration of stars and gas in the middle; a halo of sparsely distributed, old stars surrounds the disk and bulge, as do the concen- trations of stars known as globular clusters.
Stars and gas are not evenly distributed in the Milky WayΓÇÖs disk; they are in spiral arms that would look like the blades of a pinwheel if the galaxy were viewed from above. In this image, the arms appear as paths of light radiating from the center. Our Sun lies in one of these arms and orbits around the center of the Milky Way roughly once every 240 million years (a sort of ΓÇ£galactic yearΓÇ¥).
Astronomers believe the disk of the Milky Way is over 100,000 light years across and about 2,000 light years deep. The central bulge is
