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8th Universe
Term | Definition |
---|---|
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 |