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## PowerPoint Slideshow about 'Black Holes' - odell

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What happens after a SN?

- Material remaining after a supernova is 3 times more massive than the sun or more
- Pressure is strong enough to collapse the star beyond the neutron-degenerate pressure.
- Star remnant collapses and vanishes.

Characteristics of a black hole

- MATTER IN A BLACK HOLE LOSES ALMOST ALL OF ITS ORIGINAL CHARACTERISTICS!
- Retains only:
- Mass (therefore the gravity)
- Its angular momentum

*** All other characteristics no longer exist!

- concepts like protons, electrons, neutrons, molecules, compounds etc. no longer apply.

??? I have a headache.

- Escape Speed- speed needed for an object to escape the gravity of another.
- Bigger mass= bigger grav, then bigger ES
- Smaller radius= bigger grav, then bigger ES
- The escape speed for a black hole is greater than the speed of light.
- Nothing can exceed the speed of light (except Bause when he runs towards the lunch line) SO nothing can escape a BH

Singularity

- General relativity (Einstein) predicts that in creating a black hole, matter compresses to infinite density.
- ALL known laws of physics are invalid.
- Recall Relativity explains the behavior of the really massive, quantum mechanics explains the behavior of the really small (subatomic stuff). A black hole is both REALLY massive and REALLY small.

Schwarzschild radius

- The radius that matter (any matter, does it matter?) must be compressed for it to have an escape speed equal to the speed of light.
- All objects have a SR
- Earth = 1 cm or a grape
- Jupiter = 3 cm or 3 grapes (I’m not creative)
- Sun = 3 km

Event Horizon

- The location around a black hole where the escape speed EQUALS the speed of light.
- Everything in the EH is lost forever. No information can be gathered from within.
- Outside of the EH, everything appears to “slow”… called gravitational redshift

Gravitational Redshift

- Speed of light is CONSTANT through constant medium.
- In order for light to escape gravity it must work (use energy). Greater the grav, more energy.
- SO, light will lose energy and shift towards red portion of electromagnetic spectrum (longer wavelength)

Gravitational Lens

- Gravity can bend light rays.
- This can allow us to see objects normally too far for us to see.
- Bause diagram.

Infalling Matter

- Matter closest to the BH will be pulled greater, stretching the matter.
- Eventually pulled apart, atom by atom.

Does a black hole last forever?

- Nope.
- They can evaporate through Hawking Radiation (more in your lab).
- Process takes a LONG time. A 5 solar mass black hole would take 1062 years to evaporate. So, black holes that have formed, still exist today.

Supermassive Black Holes

- All elliptical and spiral galaxies seem to have one in the center. Irregular galaxies (aka dwarf galaxies) do not.
- A black hole with the mass of millions to billions of Suns!

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