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40 Cards in this Set
- Front
- Back
Flux |
A measure of the flow of energy out of a surface, usually applied to light |
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Absolute visual magnitude |
Intrinsic brightness of a star; the apparent visual magnitude the star would have if it were 10 parsecs away |
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Luminosity |
The total amount of energy a star radiates in one second |
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Hertzsprung-Russell (H-R) Diagram |
A plot of intrinsic brightness vs. Surface temperature of stars |
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Main sequence |
The region of the H-R diagram running from upper left to lower right |
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Giant |
Large, cool, highly luminous star in the mid-to-upper right of the H-R diagram |
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Supergiant |
Exceptionally luminous star whose diameter is 10 to 1,000 times greater than that of the sun |
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Red dwarf |
A faint, cool, low-mass, main-sequence star |
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White dwarfs |
Dying star that has collapsed to the size of Earth and is slowly sooling off; found in lower left of the H-R diagram |
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Stellar parallax |
A way to measure stellar distamce by how far it shifts against the background stars |
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Parsec (pc) |
The distance to a star whose parallax is one second of arc |
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Luminosity classes |
Categories of stars of similar luminosity, determined by the widths of lines in their spectra |
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Spectroscopic parallax |
Method of determining a star's distance by comparing its apparent magnitude with its absolute magnitude as estimated from its spectrum |
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Binary stars |
Pairs of stars that orbit around their common center of mass |
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Visual binary system |
A binary star system in which thr two stars are separately visible in the telescope |
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Spectroscopic binary system |
A star system in which the stars are too close together to be visible separately, but we determine that there are two stars by seeing two spectra |
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Eclipsing binary system |
A binary star system in which the stars eclipse each other |
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Light curve |
A graph of brightness vs. Time |
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Mass-luminosity relation |
The relationship which states that the more massive a main-sequence star is, the more luminous it is |
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The H-R diagram is a plot of the ______ vs the ______ of stars. |
Luminosity, temperature |
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You see a si gle point of light, but can detect thr spectra of two stars in a ____ binary system |
Spectroscopic |
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The large size of the giants and superfiants means their spectra have sharper spectra lines and their atmospheres have _________ densities |
Low |
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For main-sequence stars the greater the luminosity, the _______ the mass |
Greater |
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Red dwarfs are found in the ________ part of the H-R diagram |
Lower right-hand |
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White dwarfs are found in the _______ part of the H-R diagram |
Lower left-hand |
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The main sequence includes roughly what percentage of all normal stars? |
90% |
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The brightest luminosity class is |
Ia |
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If you moved three times farther from a star, the star would appear to be how many times fainter? |
9 |
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A light curve measures |
Brightness vs time |
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Which best deacribes the percentage of stars that are in binary systems? |
Greater than 50% |
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If you measure apparent visual magnitude and you know absolute visual magnitude, you can solve directly for the |
Distance |
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A parsec is the |
The distance to a star with a parallax of one second of arc |
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The most common spectral class of main-sequence stars is |
M |
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The most common spectral class of main-sequence stars is |
M |
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The most luminous main-sequence stars are spectral class |
O |
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The most massive main-sequence stars are spectral class |
O |
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A star has a parallax of 0.01 arc seconds. How far is it? |
100 parsecs |
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Which star has the largest diameter? |
G2 Ib |
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A star's classification is K5 III. What is the temperature of this star? |
3000 K |
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A star's classification is K5 III. What type of star is this? |
Giant |