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Unit 2 Astro 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. Together with the corona, it constitutes the star's outer atmosphere. |
| Corona | the rarefied gaseous envelope of the sun and other stars. The sun's corona is normally visible only during a total solar eclipse when it is seen as an irregularly shaped pearly glow surrounding the darkened disk of the moon. |
| 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 fact or condition of standing out from something by physically projecting or being particularly noticeable. |
| 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. Modern astronomers divide the sky into eighty-eight constellations with defined boundaries. |
| 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 | is 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 independently by Ejnar Hertzsprung (1873–1967) and Henry Norris Russell (1877–1957), in which the absolute magnitudes of stars are plotted against their spectral types. |
| Protostar | a contracting mass of gas that represents an early stage in the formation of a star, before nucleosynthesis has begun. |
| Supernova | 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. A white dwarf is formed when a low-mass star has exhausted all its central nuclear fuel and lost its outer layers as a planetary nebula. |
| Neutron Star | a celestial object of very small radius and very high density, composed predominantly of closely packed neutrons. Neutron stars are thought to form by the gravitational collapse of the remnant of a massive star after a supernova explosion, provided |
| 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. |
Created by:
Dmose
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