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GED Science
Lesson 5 The Expanding Universe
| Term | Definition |
|---|---|
| star | a globe of hydrogen and helium that produce their own heat and light through nuclear reactions |
| protostars | an early stage in the evolution of a star, after the beginning of the collapse of the gas cloud from which it is formed, but before sufficient contraction has occurred to permit initiation of nuclear reactions at its core. |
| nebula | a cloud of interstellar gas and dust |
| main-sequence star | any star lying on a diagonal band that extends from hot stars of high luminosity to cool stars of low luminosity; this is an "adult" star; the longest stage in the stellar life cycle |
| red giant | a star in an intermediate stage of evolution, characterized by a large volume, low surface temperature, and reddish hue; an "old" star |
| supernova | the explosion of a star, possibly caused by gravitational collapse, during which the star's luminosity increases by as much as 20 magnitudes and most of the star's mass is blown away at very high velocity, sometimes leaving behind an extremely dense core |
| neutron star | an extremely dense, compact star composed primarily of neutrons, especially the collapsed core of a supernova |
| white dwarf | a star, approximately the size of the earth, that has undergone gravitational collapse and is in the final stage of evolution for low-mass stars, beginning hot and white and ending cold and dark (black dwarf) |
| black hole | a theoretical massive object, formed at the beginning of the universe or by the gravitational collapse of a star exploding (supernova) whose gravitational field is so intense that no electromagnetic radiation (light) can escape. |
| Milky Way | the spiral galaxy containing our solar system. With the naked eye it is observed as a faint luminous band stretching across the heavens, composed of approximately a trillion stars, most of which are too distant to be seen individually |
| galaxy | a large system of stars held together by mutual gravitation and isolated from similar systems by vast regions of space |
| Local Group | the group of galaxies, at least 25 of which are known, that includes the Milky Way |
| universe | the totality of known or supposed objects and phenomena throughout space; the cosmos; macrocosm |
| brown dwarfs | objects that are less massive than a star but more massive than a planet; a cold, dark star that is too small to initiate the nuclear reactions that generate heat and light |
| pulsars | rotating neutron stars that emit pulses of energy at regular intervals |
| quasars | distant starlike objects that emit more energy than a hundred galaxies |
| cosmologists | scientists who study the origin, properties, and evolution of the universe |
| Big Bang Theory | one theory about the beginning of the universe; according to the theory, the universe began in a hot, superdense state smaller than an atom. A giant BANG caused all this compacted material to be flung outward, accounting for the still-expanding universe |
Created by:
jpiittmann
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