Elliptical galaxy

An elliptical galaxy is a galaxy having an approximately ellipsoidal shape and a smooth, nearly featureless brightness profile. They are one of the three main classes of galaxy originally described by Edwin Hubble in his 1936 work The Realm of the Nebulae,[1] along with spiral and lenticular galaxies. They range in shape from nearly spherical to highly flat and in size from tens of millions to over one trillion stars. Originally, Edwin Hubble thought that elliptical galaxies may evolve into spiral galaxies, which later turned out to be false.[2] Stars found inside of elliptical galaxies are very much older than stars found in spiral galaxies.[2] Most elliptical galaxies are composed of older, low-mass stars, with a sparse interstellar medium and minimal star formation activity, and they tend to be surrounded by large numbers of globular clusters. Elliptical galaxies are believed to make up approximately 1015% of galaxies in the Virgo Supercluster, but are not the dominant type of galaxy in the universe overall.[3] They are preferentially found close to the centers of galaxy clusters.[4] Elliptical galaxies are (together with lenticular galaxies) also called "early-type" galaxies (ETG), due to their location in the Hubble seque

ce, and are found to be less common in the early Universe. General characteristics High galaxies are characterized by several properties that make them distinct from other classes of galaxy. They are typically spherical or ovoid masses of old stars, starved of star-making gases. The smallest known elliptical galaxy is about one-tenth the size of the Milky Way. The motion of stars in elliptical galaxies is predominantly radial, unlike the disks of spiral galaxies, which are dominated by rotation. Furthermore, there is very little interstellar matter (neither gas nor dust), which results in low rates of star formation, few open star clusters, and few young stars; rather elliptical galaxies are dominated by old stellar populations, giving them red colours. Large elliptical galaxies typically have an extensive system of globular clusters.[5] The dynamical properties of elliptical galaxies and the bulges of disk galaxies are similar, [6] suggesting that they are formed by the same physical processes, although this remains controversial. The luminosity profiles of both elliptical galaxies and bulges are well fit by Sersic's law. Elliptical galaxies are preferentially found in galaxy clusters and in compact groups of galaxies.