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50 Cards in this Set
- Front
- Back
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Sun's spectral class
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G2V
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Solar constant
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1400 Watts/m^2
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Sun's central temp
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15,000,000 K
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Sun's surface temp
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6,000 K
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Thermonuclear fusion
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Provides energy, hydrogen burns into helium, responsible for the starlight we see
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Hydrostatic equilibrium
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balance of force of gravity and outward gas presure
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Where most of the sun's energy is generated
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Within 1/4 of the sun's radius
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Where most of the sun's visible mass is contained
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Within 60% of its visible radius
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Heat is transferred from the core to the convection zone by
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Radiation
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Heat is transferred from the convection zone to the surface by
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Convection
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How long it takes for heat to reach the surface
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Tens of thousands of years
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Neutrinos
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By-product of fusion, pass out in a couple of seconds, carry no charge, very little mass, interact very little
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Photosphere
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Produces visible surface, 6,000 K, absorption lines reveal 67 elements
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Chromosphere
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Diffuse, emission lines
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Corona
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Millions of km thick
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Granules
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Photosphere, due to convection
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Spicules
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Chromosphere, jets of surging gas
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Coronal hole
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Hole in the Sun's corona
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Sunspots
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Cool (4000 K), intense magnetic fields, reveal differential rotation
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Differential rotation
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25 day period at the equator, 35 day period near the poles
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Solar cycle
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Sunspot maximum: every 11 years, magnetic polarity reverses every 11 years
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Prominences
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Huge arching columns of cool gas above the photosphere
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Solar flares
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Violent explosions on the solar surface associated with complex sunspot groups
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Coronal mass ejection
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Giant magnetic bubbles of ionized gas that separate from the sun's atmosphere and escape into interstellar space
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Stellar parallax
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Method to measure the distance of closest stars. d (parsecs) = 1/p (in arc seconds). 1 parsec = 3.26 light-years
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Transverse (proper) motion
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Measured directly, after correcting for parallax, for nearby stars
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Radial
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Measured through Doppler effect
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True space motion
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The combination of proper motion and radial motion
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Brightness
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Apparent magnitude. Measure of the amount of light reaching Earth
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Luminosity
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Absolute magnitude. Measure of the total amount of light emitted by a star. What the apparent magnitude would be if the star was 10 parsecs away. Decreases as the inverse-square law
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Magnitude scale
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5 units=100 x brightness (or luminosity) change
1 unit= 2.5 x change Larger star means fainter to see Naked eye: 6, telescope: 30 |
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Blackbody theory
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Relates the color of the star to its surface temp (red, orange, yellow, white, blue)
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Filters
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V (visible), B (blue), U (ultraviolet)
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Hertzsprung-Russell Diagram
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Absolute magnitude vs. spectral type or luminosity vs. temp
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90% of stars are
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Main-sequence stars
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Ia
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Bright supergiants
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Ib
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Supergiants
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II
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Bright giants
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III
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Giants
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IV
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Subgiants
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V
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Main-sequence stars and dwarfs
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Binary stars
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Most stars are in a multiple star system. Stars move in elliptical orbits about a common "center of mass"
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Types of binaries
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Visual, spectroscopic, eclipsing
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Measuring orbits of binary reveals
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Mass
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Conclusion
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Luminosity proportional to (Mass)^3 for massive main-sequence stars and proportional to (Mass)^4 for more common main-sequence stars
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Combining what and what gives stellar size
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Luminosity with temp
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Total luminosity
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Area x (temp)^4
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The evolution and properties of a main sequence star is determined by
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The mass of the star
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Open (or galactic) clusters
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Loosely packed groups of young stars
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Globular clusters
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Tightly packed groups of the oldest stars known.
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