Black Holes

What is a black hole?

• A region of space from which nothing, not even light, can escape

• Has an extreme mass and density which creates an intense gravitational pull

• Distorts space and time such that space near the black hole has strange properties

The Beginnings of a Black Hole• In normal stars, the gravity

equals the internal pressure.

• As the star burns its fuel, the gravity begins to outweigh the outward pressure of the star.

• This will sometimes cause the star to collapse inward on itself, creating a black hole.

Event Horizon• Everything is not overtaken by a black hole due to an area

called the event horizon.• The event horizon is the point at which the escape velocity

equals the velocity of light.• The event horizon depends on the mass and density of the

singularity of the black hole.• The equation for the radius of the event horizon is as

follows: r=2Gm/c2

• G=gravitational constant• m=mass of black hole• c=speed of light

2/2 cGmr

Properties of Black Holes

• Mass– Can be calculated by measuring the movements of

objects around a suspected black hole• Kepler’s Modified Third Law of Planetary Motion• Rotational motion

• Electric charge• Rate of rotation

Different Types of Black Holes

1. Schwarzchild– Do not rotate and have no charge

2. Reissner-Nordstrim– Don’t rotate, but have a charge

3. Kerr– Rotate, but have no charge

4. Kerr-Newman– Rotate with a charge

Discovering Black Holes

• Cannot see them• Are found by measuring the effects on objects

around them• 3 ways to find them

– Mass estimates– Gravitational lens effect– Emitted radiation

Ways to Find Black Holes

1. Mass estimates• Black hole found if a visible star’s wobbling appears to be

caused by an invisible object (the black hole) with a mass greater than three solar masses

2. Gravitational lens effects• The huge gravity of a black hole can bend the light from

a distant object into focus

3. Emitted radiation• Superheated materials that fall into black holes emit

x-rays

Black Hole Research

• Goals of many are to find black holes and learn more about them

• Important because scientists believe that research on black holes might lead to more information on wormholes and time travel

Scientists

• A few astrophysicists who chose to study black holes

CharlesBailyn

Dr.MichaelShara

CharlesThomasBolton

Dr. AnnWehrle