An elliptical galaxy is a galaxy having an ellipsoidal shape, and a smooth, nearly featureless brightness profile. They are one of the three main types of galaxy originally described by Edwin Hubble in 1936. The others were spiral and lenticular galaxies.
Elliptical galaxies range in shape from nearly spherical to nearly flat, and in size from hundreds of millions to over one trillion stars. Originally, Edwin Hubble thought that elliptical galaxies may evolve into spiral galaxies, but this turned out to be false. Stars found inside elliptical galaxies are very much older than stars found in spiral galaxies.
Most elliptical galaxies are composed of older, low-mass stars, with a sparse interstellar medium and minimal star formation activity. They tend to be surrounded by large numbers of globular clusters. Elliptical galaxies are believed to make up approximately 10–15% of galaxies in the Virgo Supercluster, but are not the dominant type of galaxy in the universe overall. They are usually found close to the centers of galaxy clusters.
Elliptical galaxies and lenticular galaxies are also called "early-type" galaxies (ETG), due to their position in the Hubble sequence. They are less common in the early Universe, that is, in galaxies further away from us.
Related pages [change]
- IC 1101: the largest known galaxy in the universe.
- Hubble, E.P. (1936). The realm of the nebulae. New Haven: Yale University Press. ISBN 36018182.
- Loveday J. (February 1996). "The APM Bright Galaxy Catalogue.". Monthly Notices of the Royal Astronomical Society 278 (4): 1025–1048.
- Dressler A. (March 1980). "Galaxy morphology in rich clusters - Implications for the formation and evolution of galaxies.". The Astrophysical Journal 236: 351–365. doi:10.1086/157753.
- We see the furthest galaxies as they were at an earlier stage in the universe.