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Astronomy 1
Science - 9th Grade
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 | A thing that projects from something, especially a projecting feature of the landscape or a bump on a part of the body. |
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. |
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 | A 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 red giant star is a dying star in the last stages of stellar evolution. |
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-Russel 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 | 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 | The rapid expansion of matter from a state of extremely high density and temperature that according to current cosmological theories marked the origin of the universe. |