1. “For thousands more years, the mighty ships tore across the empty wastes of space and finally dived screaming onto the first planet they came across which happened to be the Earth, where due to a terrible miscalculation of scale, the entire battle fleet was accidentally swallowed by a small dog.” The Hitchhiker’s Guide to the Galaxy. Test in 1 week. Sample test/review on-line now.

2. Evolution of stars with less than 8 solar masses.
(98% of all stars)
Gravity
Fusion H to He
Gravity
Fusion He to C
Gravity
Stars < 8MSun end up as white dwarfs.
Gravity
Electron degeneracy pressure.

3. Be sure you can do this. AND that you understand why stars evolve.
The complete picture on the HR diagram.
Be sure you can do this. AND that you understand why stars evolve.

4. Stage 4b: Supernova
The Iron core cannot support itself and the star implodes/rebounds.

5. HR Diagram of the high mass side.

6. The core collapses in less than 1 second!
Iron Fusion
It takes energy to fuse Iron. So when Iron gets too hot and compressed, rather than providing energy to support the star, it begins fusion and takes energy away from the star.
The core collapses in less than 1 second!

7. Observed by Brahe in 1572

8. The complete stellar evolution flow chart
M< M>8
M<25<M

9. A Neutron Star: Main sequence mass up to 25 solar masses.
A Black Hole: Main sequence mass greater than 25 solar masses, there is no stopping the collapse. It will become a black hole.

10. The structure of neutron stars
The structure of neutron stars. A sugar lump of this matter on Earth would weigh 400 billion tons.

11. How do you detect something 20km across? Pulsars
A special kind of neutron star that "beams" radio waves in our direction.
Spin (on average) once per second.
No pulsars spin slower than every 5 seconds
Strong magnetic fields cause the "beam"

12. Neutron Stars Supported by neutron degeneracy pressure
10 to 30km across.
average mass of 1.4 solar masses.
Maximum mass of 2.5 solar masses.

13. Why do pulsars spin so fast?

14. Why don't pulsates 'pulse' longer than every 5 seconds?

18. Neutron stars can exist in pairs.

19. They have been used to (successfully) test the theory of general relativity.

20. It is estimated that our galaxy already has about 100 million neutron stars.
About 1,000 are known.

21. Neutron Stars
What happens if neutron degeneracy cannot support the star?

22. Black Holes
The end product of main sequence stars with mass greater than 25 solar masses.
Nothing can escape- not even light.

23. Black Holes Size; The black hole itself is a point at the center.
Nothing can travel faster than light.
Light travels at a fixed speed: c
Set the escape velocity (remember that?) to c and solve for size.
Schwarzchild radius: Rsch=3M for mass in solar masses you get size in kilometers.
Also called the event horizon.

24. Black Holes
The end product of main sequence stars with mass greater than 25 solar masses.
Rsch=3M for mass in solar masses and size in kilometers

26. How do you detect something that doesn't emit light?

27. Black Holes
Can exist in binaries, where they are mostly seen in X-rays.

29. X-7 in M33. The black hole is estimated at 15
X-7 in M33. The black hole is estimated at 15.7 solar masses and the star at 70 solar masses!

30. As the material gets ripped apart, it forms a disk around the black hole. This disk is slowly feeding the black hole.
However, friction within the disk makes the material very hot and bright. So although black holes themselves are dark, they are easy to find.

31. Several binaries with black holes are known.

32. From which masses have been estimated.

33. Falling into a black hole.

34. Falling into a black hole
Effect #1: Tidal forces- they're a killer!
As you get near a black hole, your feet try to fall faster than your head. This is a problem!

35. Here's poor stickman falling into a black hole
Here's poor stickman falling into a black hole. As he gets closer, he gets stretched out.

36. Falling into a black hole
But tidal forces are not the only problem. As light has to fight gravity to escape, some of its energy is lost. As light loses energy it becomes redder. So things falling into a black hole become redshifted.
The closer they get, the more redshift affects them.

37. As the rocket falls into the black hole, it gets redder, and would actually fade out of site.

38. The Wacky World of Black Holes

39. Hawking Radiation
Black holes evaporate!

41. Radiation = Light
As black holes evaporate, they emit blackbody radiation. They are luminous! E=mc2
L ~ 3.6x1032/M2 in units of W/kg2
So smaller black holes evaporate faster!
And the rate at which they evaporate increases as they lose mass.

42. Eventually, all black holes evaporate.

43. Eventually, all black holes evaporate.
If our Sun were a black hole, how long would it take to evaporate?

44. Eventually, all black holes evaporate.
What if Jupiter (0.001MSun) became a black hole, how long would it take to evaporate?

45. Eventually, all black holes evaporate.
What if Jupiter (0.001MSun) became a black hole, how long would it take to evaporate?
Still 1057 years. That’s years