ASTR 1200 Announcements

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ASTR 1200Announcements
Observing Opportunity Tonight!!Best opportunity.
Only two more chances. Last two WILL be
colder. Exams will be returned on
Thursday Problem Sets 3 and 4 posted. Due next
week.Thursday will review equations of light and
do DopplerShift. (Necessary for PS3) Second
exam will be October 28 and will cover stellar
evolutionand endpoints.
Website http//casa.colorado.edu/wcash/APS1200/AP
S1200.html
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He Compressed In Middle
H
H-gtHe
Temperature and Density Rise in Center Star gets
more luminous
He
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Electron Degeneracy

• Helium Density Rises
• Center of Sun has density of 10g/cc (H2O
  1g/cc)
• When density in center of star reaches
  30,000g/cc
• a new phenomenon kicks in
• Electron Degeneracy
• A purely quantum mechanical phenomenon

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He Flash
Star changes L and R in just 10,000 years!
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After the Flash
H
H
H-gtHe
H-gtHe
He-gtC
He-gtC
C
Helium Burns in the Center
Starts to Development Dead C Core
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Red Giants
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Nucleus
Earth Orbit
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Red Supergiant
Meanwhile, down in the core, the C is becoming
degenerate. Luminosity is becoming so great
it blows the H envelope into space.
H
H-gtHe
He-gtC
C
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Planetary Nebulae
Gas blown out into space and illuminated by
central star. The star is the degenerate C core.
The Ring Nebula
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Hourglass 2
Next Explosion is Constrained and Expands as
Hour-Glass
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Whats Left?
Eventually all the envelope is blown away. The
planetary nebula dissipates. All we have is the
hot, degenerate core. Settles down to become a
White Dwarf
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Globular Clusters
Very Old. G stars becoming giants. All the same
age and composition Can actually see evolution
off the MS
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White Dwarfs

• Held up by electron degeneracy
• About the size of the Earth R5000km
• Mass Typically 0.8M?
• Luminosity .001 L?

Thin layer of normal H
Degenerate Carbon
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Some Famous White Dwarfs

• Sirius B
• 40 Eridani B
• Procyon B

All in binaries around nearby stars. Establishes
the WD is close and small.
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Earth vs White Dwarf
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Earth vs. Sun
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Mass Radius Relation
As mass increases star gets smaller. Like ball of
foam.
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WD Density
Water has a density of 1 g/cc Lead 11 g/cc Gold
19 g/cc
100,000 times density of gold! NOT NORMAL
MATTER!!
1 cubic centimeter masses one ton!
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Surface Gravity
This is 300,000 gees
If you weigh 150lbs on Earth, you would weigh 45
million pounds on a White Dwarf!
What would happen to you and your spaceship?
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Escape Velocity
Speed of light is 3x108 m/s, so escape velocity
is .02c.