Universe 1 Astronomy 25 1 Stars 3. Dwarfs and Giants Astronomy 25 2 Stars Properties of Stars Distance Brightness Power output (luminosity) Temperature Size (radius) Mass Betelgeuse Astronomy 25 3 Stars Temperature 1. Peak of thermal spectrum 2. Brightness at two colors (B and V) 3. Spectral lines BV
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Alpha OrionisRed Supergiant (Type M)Distance: 130 pcTemperature: 3500 KMass: 14 x SunApparent V brightness: 3.6 PU (variable)Absolute V brightness: 620 PURadius: 630 x Sun = 3 AULuminosity = 63,000 x Sun!!!Hubble Space Telescope (UV)
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Stars
Size Range of Stars
Sun
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Stars Kinds of StarsThe H-R Diagram
Supergiants
Red dwarfs
Main sequence
White dwarfs
Red giants
Hertzsprung Russell
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Stars
Sirius
Binary star: A and BSirius A = Type A main sequence star
Temperature = 10,000 KTwice the mass of the Sun2.6 pc awayApparent V brightness = 24 PUAbsolute V brightness = 1.6 PU
Sun: 0.075 PU
Luminosity = 25 x SunSirius B = white dwarf
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Stars
Binary Stars
Binary stars orbit around each other.2/3 of all stars are in binary systems.
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Stars Alpha Centauri SystemThe nearest star system
A-B pair: Period = 80 yr Dist. = 11-35 AU
G2 G2 K1 M5
Proxima
A + B
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Stars
Masses of StarsThe most fundamental property of stars
mass = "weight"Only Binary (double) stars tellKepler's 3rd LawPeriod<-speed<-gravity<-mass
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Stars
Masses of Stars
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Stars
Eta Carinae
Luminous Blue VariableMass: 150 x Sun!!Luminosity: 4,000,000 x Sun!!!Temperature: 40,000 KRadius: ~100 x SunDistance: 2500 pc