Sunday, June 10, 2012
Variety of Galaxies
Using by powerful telescopes, in most galaxies only detected mixed light of all the stars, but show the closest individual stars. Galaxies come in a variety of ways. In 1930 Hubble classified galaxies into elliptical, spirals and irregulars, the first two being the most frequent.
Some galaxies have a globular shape, with a bright nucleus. They called ellipticals, contain a large population of old stars, usually little gas and dust,and some newly formed stars. Elliptical galaxies have a variety of sizes,from giant to dwarf. Elliptical galaxies Hubble symbolized by the letter E and subdivided into eight classes, from E0, almost spherical, to E7, uniformed. In elliptical galaxies the stellar concentration decreases from the core, which is small and very bright, to its edges.
Spiral galaxies are flattened disk systems containing not only some old stars but also a large population of young stars, enough gas and dust and molecular clouds are the birthplace of stars. Generally, a halo of faint older stars surrounds the disk, and there is often a smaller nuclear bulge that emits two jets of energetic matter in opposite directions. Spiral galaxies are designated with the letter S. Smaller or larger depending on development held by each arm, was assigned a letter a, b or c (Sa, Sb, Sc, SBa, SBB, SBC). There are other galaxies intermediate between elliptical and spirals, called ventricular reticular or normal identified as SO and classified in groups SO1, SO2 and SO3. In turn, we distinguish the reticular barred (SBO) which are classified into three groups based bar present more or less defined and bright.
Irregular galaxies are denoted with the letter I or IR, but usually dwarf or unusual. Fall into this group those galaxies that have no well-defined structure and symmetry. They are classified as irregular or Magellan type 1, which contain many young stars and interstellar matter, and irregular galaxies of type 2, less frequent and the content is difficult to identify. Irregular galaxies are generally located near larger galaxies, and often contain large amounts of young stars, gas and cosmic dust.
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