star - sphere of plasma held together by self-gravity, nebulae - a cloud of gas and dust in outer space; acts as a nursery for new stars, high-mass stars - more than about 8 times the mass of the Sun, low-mass stars - between about 0.08 and 8 times the mass of the Sun, protostar - a contracting mass of gas which represents an early stage in the formation of a star, main-sequence star - forms when a protostar becomes hot enough to begin hydrogen fusion; longest stage of a star’s life cycle; example: our Sun, red giant - Sun-like star; will expand in size and cool, giving it a red color, white dwarf - what stars like the Sun become after they have exhausted their nuclear fuel, supernova - massive star; a catastrophic explosion that expels almost all of the star’s material into space, black hole - an object with all its mass compressed into a single point of infinite density, neutron star - an extremely small and dense collapsed core of a massive star, Hertzsprung‐Russell Diagram - a scatter plot of stars showing the relationship between the stars' absolute magnitudes (luminosities) versus their spectral class or effective temperatures, absolute magnitudes - luminosity; measure of the brightness of a star, spectral class - the classification of stars based on their spectral characteristics, galaxies - a system of millions or billions of stars, together with gas and dust, held together by gravitational attraction, spiral galaxies - have arms that spiral outward around their center; our galaxy is a spiral galaxy called the Milky Way, elliptical galaxies - have no spiral arms and range from round to oval in shape, irregular galaxies - have shapes that lack specific definition,

8th gr Universe

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