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Unit 2 Vocab

Unit 2 Vocabulary for Astronomy (Part 2)

TermDefinition
Photosphere the region of the sun that radiates energy to space; visible surface of the sun
Chromosphere the first layer of the solar atmosphere found directly about the photosphere
Corona the outer weak layer of the solar atmosphere
Solar Wind streams of protons and electrons ejected at high speed from the solar corona
Sunspot a dark spot on the sun, which is cool by contrast to the surrounding photosphere
Prominence a concentration of gases above the solar surface that appears as bright archlike structures
Solar Flare a sudden and tremendous eruption in the solar chromosphere
Aurora a bright display of ever-changing light caused by solar radiation interacting with the upper atmosphere in the region of the poles
Nuclear Fusion the way in which the sun produces energy
Constellation an apparent group of stars orginally named for mythical characters; the sky is presently divided into 88 constellations
Binary Star one of two stars revolving around a common center of mass under their mutual gravitaional attraction
Light-year the distance light travels in a year, about 95. trillion kilometers
Apparent magnitude the brightness of a star when viewed from earth
Absolute magnitude apparent brightness of a star if it were viewed from a distance of 32.6 light-years; used to compare true brightness of stars
Main-sequence star a star that falls into the main sequence category on the H-R diagram
Red Giant a large, cool star of high luminosity
Supergiant a very large, very bright red giant star
Cepheid variable a star whose brightness varies periodically because it expands and contracts; a type of pulsating star
Nova a star that explosively increases in brightness
Nebula a cloud of gas and/or dust in space
Hertzsprung-Russell Diagram a plot of stars according to their absolute magnitudes and temperatures
Protostar a collasping cloud of gas and dust destined to become a star; a developing star not yet hot enough to engage in nuclear fusion
Supernova an exploding star that increases in brightness many thousands of times
White Dwarf a star that has exhausted most or all of its nuclear fuel and has collapsed to a very small size
Neutron Star a star of extremely high density composed entirely of neutrons
Pulsar a variable radio source of small size that emits radio pulses in very regular periods
Black Hole a massive star that has collapsed to such a small volume that its gravity prevents the escape of everything, including light
Galaxy a group of stars, dust, and gases held together by gravity
Hubble's Law a law that states that the galaxies are retreating from the Milkey Way at a speed that is proportional to their distance
Big Bang Theory the theory that proposes that the universe originated as a single mass, which subsequently exploded
Created by: DylanMcCarty22