Evolution
Current thinking is that an elliptical galaxy may be the result of a long process where two galaxies of comparable mass, of any type, collide and merge.
Such major galactic mergers are thought to have been common at early times, but may carry on more infrequently today. Minor galactic mergers involve two galaxies of very different masses, and are not limited to giant ellipticals. For example, our own Milky Way galaxy is known to be "ingesting" a couple of small galaxies right now. The Milky Way galaxy is also, depending upon an unknown tangential component, on a collision course in 4-5 billion years with the Andromeda Galaxy. It has been theorized that an elliptical galaxy will result from a merger of the two spirals.
Every bright elliptical galaxy is believed to contain a supermassive black hole at its center. The mass of the black hole is tightly correlated with the mass of the galaxy, via the M-sigma relation. It is believed that black holes may play an important role in limiting the growth of elliptical galaxies in the early universe by inhibiting star formation.
Read more about this topic: Elliptical Galaxy
Famous quotes containing the word evolution:
“As a natural process, of the same character as the development of a tree from its seed, or of a fowl from its egg, evolution excludes creation and all other kinds of supernatural intervention.”
—Thomas Henry Huxley (1825–95)
“The more specific idea of evolution now reached is—a change from an indefinite, incoherent homogeneity to a definite, coherent heterogeneity, accompanying the dissipation of motion and integration of matter.”
—Herbert Spencer (1820–1903)
“The evolution of sense is, in a sense, the evolution of nonsense.”
—Vladimir Nabokov (1899–1977)