stars - fatcow
TRANSCRIPT
Universe 1
Astronomy 25 1
Stars
3. Dwarfs and Giants
Astronomy 25 2
Stars
Properties of Stars
DistanceBrightnessPower output (luminosity)TemperatureSize (radius)Mass
Betelgeuse
Astronomy 25 3
Stars
Temperature1. Peak of thermal
spectrum2. Brightness at two
colors (B and V)3. Spectral lines
B V
Universe 2
Astronomy 25 4
Stars
Spectral TypesO 40,000 KB 20,000 KA 10,000 KF 7,000 KG 5,500 KK 4,500 KM 3,500 KL 2,000 KT 1,000 K Oh Be A Fine Girl/Guy Kiss Me
Hβ
Sodium D
Hγ
Calcium H & K
Hα
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Stars
2-D Plot
What are weseeing?
Astronomy 25 6
Stars
H-R DiagramNearby Stars
Universe 3
Astronomy 25 7
Stars
Barnard’s Star In Ophiuchus Highest proper motion
10” per year Red dwarf
Type M main sequence starTemperature: 3100 K
Distance: 1.8 pc2nd to Alpha Centauri
Apparent V brightness: 0.001 PU Absolute V brightness: 0.00003 PU Luminosity: 0.0004 x Sun Mass = 0.15 x Sun
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Stars
H-R DiagramBright Stars
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Stars
Size of Stars
Stefan's LawL = σT4A= (const.)(temperature)4(area)
area<->radiusLuminosity<->temperature<->radius
Universe 4
Astronomy 25 10
Stars
Betelgeuse
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
Universe 5
Astronomy 25 13
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
Universe 6
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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
Hubble Space Telescope
Universe 7
Astronomy 25 19
Stars
The Main Sequence
Mass determines placementon the Main Sequence
High mass→high temperaturevery high
luminosityshort lifetime!
Low mass→ ?
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Stars
Practice Question
Q. Which star isthe mostmassive?
1. A2. B3. C4. D
BA
C
D
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Stars
What Happens Next?