1. Exams will be returned on Thursday
ASTR 1200 Announcements
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 Doppler Shift. (Necessary for PS3)
Second exam will be October 28 and will cover stellar evolution and endpoints.
Website

2. He Compressed In Middle
H->He
Temperature and Density
Rise in Center
Star gets more luminous He

3. Electron Degeneracy 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

4. He Flash
Star changes L and R
in just 10,000 years!

5. After the Flash H H H->He H->He He->C
Helium Burns in the Center
Starts to Development Dead C Core

6. Red Giants

7. Nucleus
Earth Orbit

8. 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->He
He->C C

9. Planetary Nebulae Gas blown out into space and
illuminated by central star.
The star is the degenerate C core.
The Ring Nebula

10. Hourglass 2
Next Explosion is
Constrained and Expands
as Hour-Glass

11. What’s 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

12. Globular Clusters Very Old. G stars becoming giants.
All the same age and composition
Can actually see evolution off the MS

13. White Dwarfs Held up by electron degeneracy
About the size of the Earth R~5000km
Mass Typically 0.8M
Luminosity ~ .001 L
Thin layer of “normal” H
Degenerate Carbon

14. Some Famous White Dwarfs
Sirius B
40 Eridani B
Procyon B
All in binaries around nearby stars.
Establishes the WD is close and small.

15. Earth vs White Dwarf

16. Earth vs. Sun

17. Mass Radius Relation As mass increases star gets smaller.
Like ball of foam.

18. WD Density 1 cubic centimeter masses one ton!
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!

19. 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?

20. Escape Velocity
Speed of light is 3x108 m/s, so escape velocity is .02c.