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Vocab Astron part 2
Term | Definition |
---|---|
Photosphere | the luminous envelope of a star from which its light and heat radiate. |
Chromosphere | 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 | spot or patch appearing from time to time on the sun's surface, appearing dark by contrast with its surroundings. |
Prominence | a stream of incandescent gas projecting above the sun's chromosphere. |
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 |
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, which is 9.4607 × 1012 km (nearly 6 trillion miles). |
apparant 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 | Main sequence stars fuse hydrogen atoms to form helium atoms in their cores. |
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. |
cepheid 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. |
nebula | 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 | 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 |
nuetron star | a celestial object of very small radius (typically 18 miles/30 km) 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. |
hubbles law | Hubble's law is the name for the observation in physical cosmology that: Objects observed in deep space (extragalactic space, ~10 megaparsecs or more) are found to have a Doppler shift interpretable as relative velocity away from the Earth |
big bang theory | leading explanation about how the universe began. |