**Black Holes**

Katharine Santiago

**History**

In 1686, Isaac Newton published his universal laws of Gravity.

In 1783, one of Britain's leading scientists, John Mitchell, made a suggestion that some stars may have so much surface gravity that not even light can escape them.

Mitchell's theory was ignored by many 19th century scientists because they believed that light was not affected by gravity.

In 1915, Albert Einstein expands his theory of relativity to account for the affects of gravity. He showed through his equations that gravity is a warp in space time. The bigger the object, the greater the warp in space time would be.

In 1916, scientist Karl Schwarzschild found a solution to Einstein's field equations. He found that one or more terms in Einstein's equations was infinite. In this case it meant that a large dying star would collapse in on itself until it formed a central singularity. The meaning of these mathematical equations was not well understood at the time and many scientists did not believe that a massive body could collapse into an infinitely dense point.

It isn't until 1967 that physicist John Wheeler comes up with a name for these collapsed stars: black holes.

What is a Black Hole

A black hole is a region in space with such a great amount of mass that nothing can escape its gravitational pull, not even light.

There are two types of black holes: Stellar black holes and supermassive black holes

The three numbers needed to describe a black hole are mass, charge, and angular momentum.

Black holes have four main parts to them: Singularities, the event Horizon, the ergosphere, and the accretion disk.

1: Singularity

2: Event Horizon

3: The Ergosphere

4: Accretion Disk

A rapidly spinning disk of gas and dust that surrounds a celestial object with an intensely strong gravitational pull.

Once an object crosses the event horizon it cannot cross back, because the escape velocity is greater than the velocity of light.

The point where all matter and energy is compressed. It has no size and infinite density. There is no way for scientists to find it.

The region outside of the event horizon where gravity starts to effect the movement of objects in space. Objects in space don't accelerate, but when they reach the ergosphere, they appear to slow down. This is known as time dilation.

How a Black Hole Is Formed

As long as a star continues to emit radiation, it can match the force of gravity. When the star's outward pressure (caused by tempurature) becomes smaller, the gravity will become too strong, causing the star to collapse on itself.

This is the main way for a black hole to form

They can also form when two dense objects, like neutron stars, collide

Physics Behind Black Holes

Artist's impression of a dust-bound supermassive black hole

www.spacetelescope.org/images/heic0409a/

When a body is outside the gravitational pull, both kinetic and potential energy are equal to zero. The equation would look like this:

M is the mass of the body or planet

m is the mass of the object trying to escape

r is is the radius of the planet/body

G is the gravitational pull

To solve for the escape velocity, you would rewrite the equation to look like this:

In Order for a black hole to form, it must be below a certain radius. This radius can be found by the following equation:

Sources

cosmology.berkely.edu/education

www.astronomy.com

blackholes.stardate.org

Dictionary.reference.com

www.astronomysource.com

www.universetoday.com

www.outerspacecentral.com/black_holes_page

http://www.cosmotography.com

Physicsforidiots.com/space

V is the escape velocity

G is the gravitational pull

M is the mass of the planet or body

r is the radius of the planet/body

R is the radius. It is called the Schwartzschild radius.

G is the force of gravity

c is the speed of light

If you had two stars with the same values for M, Q, and J, but one was made of matter, and the other of antimatter, when the two stars collapsed into black holes, they would be identical. All other information would be lost behind the event horizon.