The Sb Galaxies: Milky Way-Like Galaxies
The Milky Way galaxy probably looks like the Sb galaxies shown below. Sb's show fairly extensive arms, yet a reasonably large and luminous central bulge. About 15% of the visible mass is in cold gas and dust. Star formation is seen along the arms as very bright knots of HII regions. Sb galaxies have a fairly massive Pop II stellar bulge component and an extended halo of Globular Clusters, similar to what is seen in our own galaxy.
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M81 is an Sb galaxy 12 million light years away. |
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M31 is an Sb galaxy about 1 million light years away. This is the largest galaxy in our Local Group of galaxies. Our own galaxy, the Milky Way, is a close second in size to M31. |