A galaxy is a gravitationally bound object compounding of interstellar gas and dust, stars, star remnants, and dark matter (Wikipedia). There are three different types of galaxies all galaxies are categorized in: elliptical, spiral, and irregular. In the visible Universe alone at least 2 trillion galaxies exist, with many believed to have black holes in the center. In between galaxies is just copious amounts of space with gas aimlessly floating around. In terms of size, galaxies can range anywhere from 1,000 parsecs (1 parsec is approximately 3.3 light years) to 100,000 parsecs! Thus, galaxies come in all shapes and sizes.
Elliptical galaxies are often shaped like a stretched out sphere. From pictures, their obvious oval shape often gives them away. They are measured by their ellipticity, or how elongated they are from a perfect circle. The greater the ellipticity, the more elliptical the galaxy is. The galaxies rotate around no specific axis. Spiral galaxies are classified from three components: a bulge, a disk, and a halo. The bulge is the center of a galaxy where much older stars can be found. The disks which make up the swirly structure of a spiral galaxy are loaded with gas and dust, and teeming with young stars. Lastly, the halo of a galaxy is more gas and dust loosely surrounding the bulge and some disks. It contain globular clusters, or tight-knit groups of stars. A common example of a spiral galaxy is our own home: the Milky Way galaxy! Irregular galaxies have an unpredictable structure and are often asymmetrical. There are two groups of irregular galaxies: Irr I and Irr II. Irr I has a lot of hydrogen gas present as well as many young stars. Irr II just have great amounts of dust blocking light from shining through. Sources: "Galaxy." Wikipedia. Wikimedia Foundation, 6 Jan. 2017. Web. 09 Jan. 2017. <https://en.wikipedia.org/wiki/Galaxy>. McNally, Erin. "Types and Classification of Galaxies." CLASSIFICATION. Cornell University, 18 Apr. 2000. Web.09Jan.2017. <http://www.astro.cornell.edu/academics/courses/astro201/galaxies/types.htm>.
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AuthorAn aspiring amateur astronomer. 18. Pomfret School '17 | BU '21. ArchivesCategories |