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23 Cards in this Set

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absolute visual magnitude (Mv)
Intrinsic brightness of a star. The apparent visual magnitude the star would have if it were 10 pc away. (p. 149)
binary stars
Pairs of stars that orbit around their common center of mass. (p. 157)
bipolar flow
Jets of gas flowing away from a central object in opposite directions. Usually applied to protostars. (p. 167)
birth line
In the H-R diagram, the line above the main sequence where protostars first become visible. (p. 165)
Bok globule
Small, dark cloud only about 1 ly in diameter that contains 10 to 1000 solar masses of gas and dust. Believed to be related to star formation. (p. 166)
eclipsing binary system
A binary star system in which the stars eclipse each other. (p. 160)
flux
A measure of the flow of energy out of a surface. Usually applied to light. (p. 149)
giant
Large, cool, highly luminous star in the upper right of the H-R diagram. Typically 10 to 100 times the diameter of the sun. (p. 152)
H-R diagram
See Hertzsprung-Russell diagram.
Hertzsprung-Russell (H-R) diagram
A plot of the intrinsic brightness versus the surface temperature of stars. It separates the effects of temperature and surface area on stellar luminosity. Commonly plotted as absolute magnitude versus spectral type but also as luminosity versus surface temperature or color. (p. 151)
light curve
A graph of brightness versus time commonly used in analyzing variable stars and eclipsing binaries. (p. 160)
luminosity (L)
The total amount of energy a star radiates in 1 second. (p. 149)
luminosity class
A category of stars of similar luminosity, determined by the widths of lines in their spectra. (p. 153)
main sequence
The region of the H-R diagram running from upper left to lower right, which includes roughly 90 percent of all stars. (p. 152)
mass-luminosity relation
The more massive a star is, the more luminous it is. (p. 162)
parsec (pc)
The distance to a hypothetical star whose parallax is 1 second of arc. 1 pc = 206,265 AU = 3.26 ly. (p. 147)
red dwarf
A faint, cool, low-mass, main sequence star. (p. 153)
spectroscopic binary system
A star system in which the stars are too close together to be visible separately. We see a single point of light, and only by taking a spectrum can we determine that there are two stars. (p. 158)
spectroscopic parallax
The method of determining a star's distance by comparing its apparent magnitude with its absolute magnitude as estimated from its spectrum. (p. 154)
stellar parallax (p)
A measure of stellar distance. See also parallax. (p. 147)
supergiant
Exceptionally luminous star whose diameter is 10 to 1000 times that of the sun. (p. 152)
visual binary system
A binary star system in which the two stars are separately visible in the telescope. (p. 156)
white dwarf
Dying star that has collapsed to the size of Earth and is slowly cooling off. At the lower left of the H-R diagram. (p. 153)