Goal: To understand special stars.

Goal: To understand special stars. Objectives: To learn the basics about Black holes To examine the different sizes/masses of Black holes To learn about the physics inside a black hole To explore Kerr black holes. To explore Hawking Radiation To learn about some other black hole oddities

What is a black hole • As we saw before an object dense enough or massive enough such that the escape velocity is the speed of light

Event Horizon • = Goodbye Forever (takes infinite time to pass through it) • Is the surface where the escape velocity is the speed of light • Is the effective radius of the black hole • Rs = 1.5 km * Mass of black hole (in solar masses)

However • Black holes are very rare. • They also come in many sizes/masses.

Solar Mass Black Holes • These are black holes that are 5-50 times the mass of our sun. • They are formed from the deaths of massive stars. • If on their own they are very tough to find as we can only see black holes when they interact with other objects.

Black Holes in binaries • Just like with Neutron stars and white dwarfs, black holes will create an accretion disk. • However, you can see nothing from the actual accretion, so all you get to see is the accretion disk. • On the plus side, the accretion disk goes down to a few km in size at which point the gas has been heated quite a bit (infalling gas is slowed by frictional heating and interactions with the magnetic field). • The innermost parts will emit X-rays!

Black holes in Globular Clusters • In the centers of Globular Clusters, where stars are very tightly packed we often find black holes • These black holes can be a few thousand times the mass of our sun. • There also seems to be a correlation between cluster mass and black hole mass.

Galactic Center Black Holes • Every galaxy we can peer into its center has a black hole that is millions of solar masses to billions. • Ours is 4 million. • Andromeda is about a billion.

Astro-mercial • But wait there’s more! • JETS! • Materials racing outward at close to the speed of light and going for up to millions of light Years! • (NGC 5532)

Physics outside a black hole • We have 4 known dimensions • 3 real spatial • 1 real time • Real Distance = Real Velocity * Real Time • Real Acceleration = Change in Real Velocity / Real Time

Inside a black hole: • Tobject = Tuniversal / (1 – rs / r)1/2 • So, when r > Rs then we have the square root of a negative number. • What does that give us?

Imaginary Time • So, time is not real but in terms of i (i = square root of -1) • In our 4 dimensional physics world this messes up everything… • So how can the Laws of Physics not work and still be Laws?

Maybe not • M-Theory (not really a “Theory” more a “Model”, but M-Model does not sound impressive) • 11 dimensions • So, what makes no sense in 4 dimensions might make sense in 11. • (so might have 3 real spatial, 3 imaginary spatial, real time, imaginary time, and 3 more dimensions)

So • Black Holes may have a key in unlocking the mysteries of the universe. • However, we have no idea what happens to the stuff inside the black hole. • Does it all collapse to center, or just get converted to energy?

Properties • Even though the physics fail as we currently understand them in our 4 D worldview Black Holes still have properties • They have magnetic fields • Some have spin.

Kerr Black Holes • Kerr Black Holes are black holes with spin. This gives them a different structure

Spin Energy • In the distant future you can actually take the spin energy out of a Kerr Black Hole and use it! • However the closest black hole is > 1000 light years away so…

Oddity • Too much spin and the event horizons go away • This would create a “naked singularity”

Hawking’s Radiation • Space is NOT empty, it has energy! • Everywhere in space you are constantly forming pairs of particles. • One with + energy, one with -. • They usually run into other particles and destroy themselves.

Near an event horizon • There is a chance for the negative energy particle to quantum tunnel through the event horizon and end up inside the black hole • The positive energy particle then escapes from the black hole (making it appear that the particle came from inside the black hole) • Since energy is mass that means the black hole looses mass!

However • This process for known black holes will not start (due to getting more energy from the universe and radiation from the universe than they would loose) for a long time • The smaller black holes will last a google years. • The bigger ones even longer.

Wormholes + White Holes • If you bend space time enough it makes it very easy to get to another place • Black holes are one way to do that • However, it is problematic • White holes are the opposite. • You go into a black hole, and shoot out a White hole. • Warning: the white hole you exit would not be in our universe but would be in a negative space universe • 2nd warning: UNSTABLE! Just you entering might be enough to destablize

Conclusion • We have learned a whole lot about black holes. • They exist and are here and there, but are rare. • They come in more than 1 flavor • They might be pointing towards other areas/laws of Physics

Goal: To understand special stars.