Friday, May 9, 2008

Types of Stars: Giants and Dwarfs

Stars come in a variety of sizes, temperatures and luminosities. The biggest stars are supergiants and hypergiants. These heavy stars fuse heavier elements than the ordinary Hydrogen and Helium. Although these stars have the hottest cores, their outer edges are very cool (the lowest only about 2000 K), and they also are the least luminous. The largest star on record is the star VY Canis Majoris. It is a hypergiant has a diameter 1800 times that of the Sun! In comparison, if the Sun was replaced with VY Canis Majoris, its outer edges would extend past the orbit of Saturn. Giants are always red or orange. These stars burn their fusion supply so quickly, that they only live for about 10 million years sometimes.

Other stars of this faint luminosity include: white dwarfs, brown dwarfs and black dwarfs (same as white dwarfs but totally cooled off). A brown dwarf is a special case of star where the temperature doesn't get high enough to start Hydrogen fusion, but high enough to do either deuterium (Hydrogen with a neutron and a proton) fusion (lower limit for this fusion is 13 Jupiter masses), or Lithium fusion (lower limit 65 Jupiter masses). These stars also have extremely long lives. They can live for trillions (not billions, trillions) of years!!!!!

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