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Astronomy Vocab 2
| Term | Definition |
|---|---|
| Photosphere | the luminous envelope of a star from which its light and heat radiate |
| Chromosphere | a reddish gaseous layer immediately above the photosphere of the sun or another star |
| Corona | the rarefied gaseous envelope of the sun and other stars |
| Solar Wind | the continuous flow of charged particles from the sun that permeates the solar system |
| Sunspot | a spot or patch appearing from time to time on the sun's surface, appearing dark by contrast with its surroundings |
| Prominence | the state of being important or famous |
| 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 |
| Nuclear fusion | a nuclear reaction in which atomic nuclei of low atomic number fuse to form a heavier nucleus with the release of energy |
| Constellation | a group of stars forming a recognizable pattern that is traditionally named after its apparent form or identified with a mythological figure |
| Binary star | a system of two stars in which one star revolves around the other or both revolve around a common center |
| Light-year | a unit of astronomical distance equivalent to the distance that light travels in one year, which is 9.4607 × 1012 km (nearly 6 trillion miles) |
| Apparent magnitude | the magnitude of a celestial object as it is actually measured from the earth |
| Absolute magnitude | the magnitude (brightness) of a celestial object as it would be seen at a standard distance of 10 parsecs |
| Main-sequence star | any star that is fusing hydrogen in its core and has a stable balance of outward pressure from core nuclear fusion and gravitational forces pushing inward |
| Red Giant | a very large star of high luminosity and low surface temperature, Red giants are thought to be in a late stage of evolution when no hydrogen remains in the core to fuel nuclear fusion |
| Supergiant | a very large star that is even brighter than a giant, often despite being relatively cool |
| Nova | a star showing a sudden large increase in brightness and then slowly returning to its original state over a few months |
| Hertzsprung-Russell Diagram | a two-dimensional graph, devised by Ejnar Hertzsprung (1873–1967) and Henry Norris Russell (1877–1957), in which the absolute magnitudes of stars are plotted against their spectral types. Stars are found to occupy only certain regions of such a diagram |
| Protostar | a contracting mass of gas that represents an early stage in the formation of a star, before nucleosynthesis has begun |
| Supernova | a star that suddenly increases greatly in brightness because of a catastrophic explosion that ejects most of its mass |
| White dwarf | a small very dense star that is typically the size of a planet |
| Neutron star | a celestial object of very small radius (typically 18 miles/30 km) and very high density, composed predominantly of closely packed neutrons |
| Black hole | a region of space having a gravitational field so intense that no matter or radiation can escape |
| Galaxy | a system of millions or billions of stars, together with gas and dust, held together by gravitational attraction |
| 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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