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What Kind of Galaxies are there? ... They are scattered throughout the universe, and astronomers estimate that there are between 50 and 100 galaxies all tolled. ... Large galaxies have more than a trillion stars, while smaller ones have fewer than a billion. Galaxies are distributed unevenly throughout space. ... Clusters of galaxies range in size from a few dozen members to several thousand. There are three main types of galaxies. These types are called spiral galaxies, elliptical galaxies, and irregular galaxies. Some galaxies are also classified as radio galaxies, seyfert galaxies, and X-ray galaxies. ... About 17 percent of the galaxies that astronomers observe are spiral in shape, however, of the 1,000 brightest galaxies, over 70 percent are classified as spiral. ... Spiral galaxies contain not only some old stars, but also large populations of young stars, much gas and dust, and molecular clouds that are the birthplace of stars. ... Classification of spiral galaxies ranges from tightly packed spiral arms (SA or SBA) to loosely packed arms (SC or SBC), depending on whether they are a normal spiral (arms wind around each other) or barred spiral (arms stay apart from each other). ... This is characteristic of all spiral galaxies. Among other spiral galaxies, the Andromeda galaxy, at a distance of 2. ...
Elliptical galaxies range in shape from almost perfect spheres to flattened globes. Eighty percent of all galaxies are elliptical, with no spiral arms and little or no visible structure. They are found in a vast range of sizes, but are generally the largest galaxies in the universe. ... Such galaxies contain a very large population of old stars, usually with little apparent gas or dust, and few newly formed stars. The reason for this irregularity is that it is believed that supernovas, which occur much more frequently in elliptical galaxies, keep these galaxies clean of interstellar gas and dust, and thus prevent the formation of new stars.
Approximate Word count = 1469
Approximate Pages = 5.9
(250 words per page double spaced)
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