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Astronomy Part 2
The vocab for the 2nd part of astronomy
| Term | Definition |
|---|---|
| photosphere | the luminous visible surface of the sun, being a shallow layer of strongly ionized gases |
| chromosphere | a scarlet, gaseous envelope surrounding the sun outside the photosphere, from which enormous quantities of hydrogen and other gases are erupted |
| corona | a white or colored circle or set of concentric circles of light seen around a luminous body, especially around the sun or moon |
| solar wind | an emanation from the sun's corona consisting of a flow of charged particles, mainly electrons and protons, that interacts with the magnetic field of the earth and other planetary bodies |
| sunspot | one of the relatively dark patches that appear periodically on the surface of the sun and affect terrestrial magnetism and certain other terrestrial phenomena |
| prominence | an eruption of a flamelike tongue of relatively cool, high-density gas from the solar chromosphere into the corona where it can be seen during a solar eclipse or by observing strong spectral lines in its emission spectrum |
| solar flare | a brief eruption of intense high-energy radiation from the sun's surface, associated with sunspots and causing electromagnetic disturbances on the earth, as with radio frequency communications and power line transmissions |
| aurora | an atmospheric phenomenon consisting of bands of light caused by charged solar particles following the earth's magnetic lines of force |
| nuclear fusion | a thermonuclear reaction in which nuclei of light atoms join to form nuclei of heavier atoms, as the combination of deuterium atoms to form helium atoms |
| constellation | any of various groups of stars to which definite names have been given, as Ursa Major, Ursa Minor, Boötes, Cancer, Orion |
| binary star | a system of two stars that revolve about their common center of mass |
| light-year | the distance traversed by light in one mean solar year, about 5.88 trillion mi. (9.46 trillion km): used as a unit in measuring stellar distances |
| apparent magnitude | the magnitude of a star as it appears to an observer on the earth |
| absolute magnitude | the magnitude of a star as it would appear to a hypothetical observer at a distance of 10 parsecs or 32.6 light-years |
| main-sequence star | any star lying on a diagonal band that extends from hot stars of high luminosity to cool stars of low luminosity |
| red giant | a star in an intermediate stage of evolution, characterized by a large volume, low surface temperature, and reddish hue |
| supergiant | an exceptionally luminous star whose diameter is more than 100 times that of the sun |
| cepheid variable | a variable star in which changes in brightness are due to alternate contractions and expansions in volume |
| nova | a star that suddenly becomes thousands of times brighter and then gradually fades to its original intensity |
| nebulae | a cloud of interstellar gas and dust |
| Hertzsprung-Russell Diagram | the graph showing the absolute magnitude plotted against the surface temperature for a group of stars |
| protostar | 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 |
| 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 |
| 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 |
| neutron star | an elementary particle having no charge, mass slightly greater than that of a proton |
| pulsar | one of several hundred known celestial objects, generally believed to be rapidly rotating neutron stars, that emit pulses of radiation, especially radio waves, with a high degree of regularity |
| black hole | a theoretical massive object, formed at the beginning of the universe or by the gravitational collapse of a star exploding as a supernova, whose gravitational field is so intense that no electromagnetic radiation can escape |
| galaxy | a large system of stars held together by mutual gravitation and isolated from similar systems by vast regions of space |
| Hubble's law | the law that the velocity of recession of distant galaxies from our own is proportional to their distance from us |
| Big Bang Theory | a theory that deduces a cataclysmic birth of the universe (big bang) from the observed expansion of the universe, cosmic background radiation, abundance of the elements, and the laws of physics |
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