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Part 2 Vocab
Atronomy
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 sta |
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. |
Prominience | 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 |
aurora | a natural electrical phenomenon characterized by the appearance of streamers of reddish or greenish light in the sky |
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 (6 trillion miles) |
Apparent magnitude | the magnitude of a celestial object as it is actually measured from the earth. |
Absolute magnitude | he 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 |
supergiant | a very large star that is even brighter than a giant, often despite being relatively cool. |
cephied variable | a variable star having a regular cycle of brightness with a frequency related to its luminosity, so allowing estimation of its distance from the earth |
nova | a star showing a sudden large increase in brightness and then slowly returning to its original state over a few months. |
Nebulae | a cloud of gas and dust in outer space, visible in the night sky either as an indistinct bright patch or as a dark silhouette against other luminous matter. |
Hertzsprung-Russell diagram | 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. 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. 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. |
nuetron star | a celestial object of very small radius and very high density, composed predominantly of closely packed neutrons |
pulsar | a celestial object, thought to be a rapidly rotating neutron star, that emits regular pulses of radio waves and other electromagnetic radiation at rates of up to one thousand pulses per second. |
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. |
hubble's law | A law of cosmology stating that the rate at which astronomical objects in the universe move apart from each other is proportional to their distance from each other. |
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. |