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Vocab Astron part 2

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.
Created by: Alex Kidd