Fig12_8 Andromeda Nebula

Fig12_8 Andromeda Nebula

Fig. 12.8 . The nearest spiral galaxy, the Andromeda Nebula, also known as M 31 and NGC 224, is located at a distance of about 2.6 million light-years, so its light takes about 2.6 million years to reach us. Both the Andromeda Nebula and our Galaxy are spiral galaxies with total masses of about a million million, or 1012, solar masses, and roughly a hundred billion, or 1011, optically visible stars. The several distinct stars surrounding the diffuse light from Andromeda are stars within our own Galaxy; these stars lie well in front of Andromeda. Two smaller galaxies are also shown in this image. They are M 32, also designated as NGC 221, shown at the edge of the Andromeda Nebula, and NGC 205, that is located somewhat further away. These are elliptical systems at about the same distance as M 31, but with only about one-hundredth of its mass. (Courtesy of Karl-Schwarzschild Observatorium, Tautenburg.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University