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ELL Earth Sci 27.1/2
Star Characteristics & Evolution
Term | Definition |
---|---|
star | a body of gas that gives off a tremendous amount of radiant energy in the form of light and heat |
circumpolar | describing any star that is always visible in the night sky and, from the Northern Hemisphere, can be seen circling Polaris |
Polaris | the north star, which is found at the tip of the tail of the Little Dipper (Ursa minor) |
parallax | a method of determining the distance from the Earth to star based upon the shift of apparent position when viewed from angles |
magnitude | the brightness of a star |
apparent magnitude | brightness of a star as it appears from the Earth |
absolute magnitude | brightness of a star as it would appear if located 32.6 light-years from Earth |
parsec | a unit of distance used in astronomy, equal to about 3.26 light-years |
H-R Diagram | Hertzsprung-Russell diagram; graph showing the relationship of surface temperature and absolute magnitude of a star |
nebula | dark cloud of gas and dust in space; 1st stage in the evolution of a star, which results in a protostar |
main sequence star | star with characteristics that place it within a band running through the middle of a the H-R Diagram; 2nd stage in the evolution of a star |
red giant / red supergiant | very large star resulting from its using up its hydrogen for fusion, collapsing, heating and expansion; 3rd stage in the evolution of a star |
white dwarfs | small, very hot star resulting from a giant star, which collapses due to lack of fusion and loses its outer layers; 4th stage in the evolution of a star |
plasma | 4th state of matter; found inside a star where the gases are so heated that they lose their electrons are torn from the parent atom and float freely |
nuclear fusion | the squeezing of atomic nuclei together due to extensive heat and pressure; usually hydrogen atoms are converted to helium inside the star's core |
planetary nebula | expanding shell of gases shed by a dying star |
nova | white dwarf star that explodes as it cools, temporarily becoming thousands of times brighter |
supernova | star that blows apart with a tremendous explosion |
neutron star | collapsed core of a supernova consisting of a small, extremely dense ball of neutrons |
pulsar | neutron star that spin and emit two beams of radiation that sweep across space |
black hole | hole in space with a gravity so great that not even light can escape; formed by the collapse of a very large supernova |