Black Holes

This one’s green.I like green.

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.

All galaxies… ranging from 3 bill. ly to 9 bill ly.

Sphagettification?

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!