AP BIOLOGY

Detailed explanation-1: -The bulge at the center of our galaxy lies somewhere in the middle: The bulge contains mostly reddish stars. Many of them are relatively old–ten billion years or more. At the very center of the bulge is a supermassive black hole, but it doesn’t have much of an effect outside of its immediate vicinity.

Detailed explanation-2: -The Sun is found in the disk, but, as Shapley found, we are about 8, 000 parsecs from the center. The dimensions of the disk are similar in ratio to an old vinyl record. That is, the thickness is much smaller than the radius. Besides stars, the disk contains the majority of the gas and dust in the Milky Way.

Detailed explanation-3: -All the bright, blue stars visible in our sky are part of the Galactic disk, as are the young open star clusters and star-forming regions. In contrast, the cooler, redder stars-including those found in the old globular clusters-are more uniformly distributed throughout the disk, bulge, and halo.

Detailed explanation-4: -As their name suggests, elliptical galaxies are round or oval, with stars distributed fairly uniformly throughout. They have a bulge and halo, like spiral galaxies, but don’t have the flat disk of stars. The stars in ellipticals tend to be older.