““BLACK HOLES”BLACK HOLES”

Luna Marisol Strunk Catalina Salvà Mas1er Batxiler

A look through Black Holes' history

Albert Einstein first predicted black holes in 1916 with his general theory of relativity. The term "black hole" was coined in 1967 by American astronomer John Wheele.

The first one was discovered in 1971. It was the binary star Cygnus X-1. Its effect on its companion star suggested that it must be a compact object with a mass too high for it to be a neutron star.

In 1974 Stephen Hawking combined theories of General Relativity and Quantum Mechanics to show that black holes radiate energy. Although initially ridiculed, this is now generally accepted in the field of astro-physics.

In 1783, Jhon Michell conjectured that there might be an object massive enough to have an espace velocity grater than the speed of light

But...What are they?They are regions in space where the gravitational attraction is so strong that even light cannot get out.

They are caused by a very dense mass that has already pilled up.

We can't think of a black hole as the usual meaning of “black hole”. They aren't totally balck and they aren't holes at all, instead they are regions where neither light nor matter can escape.

They don't have any grater gravitational reach than any other star of the same mass.

Structure of Black Holes

● There is a region of space surrounding the black hole from where light cannot escape. It's called the Event Horizon. It's the point where the escape velocity from the gravitational field is equal to the speed of light. Is the place farthest away from the middle where the gravity is still strong enough to trap light.

● The Singularity is the gravitational center in the middle of the black hole.

● The event horizon's radius is called the Schwarzschild Radius

● The Accretion Disk is a disk composed of stellar material that is spiraling towards the black hole.

● The Ergosphere is the cape surrounding the black hole. If the black hole is rotating, then as it spins, its mass causes the space time around the black hole to rotate as well.

● Jets of Gas. For some black holes high intensity magnetic fields are emitted perpendicular to the accretion disk. This causes charged particles to circle these magnetic field lines and creates jets of gas perpendicular to the acceleration disk.

TYPES

OF

BLACK

HOLES

Supermassive black holes: they are the largest ones. Their masses are more than 1 million suns together. In every large galaxy there is a supermassive black hole in its center. The supermassive black hole in the centre of the Milky Way is called Sagittarius A. Its mass is equal to 4 million suns together.

Stellar black holes: they are the most common black holes. They have a mass that can be 20 times more than the mass of the sun. In the Milky Way there are many of them.

● Micro black holes: their masses are as small as 20 micrograms. They exist in theory, but have no directly detected. It is thought that they are all around our atmosphere.

Formation of Black HolesStellar black holes are made when the center of a very big star falls in upon itself or collapses and this causes a supernova, leaving a black hole core behind where the star once exist.

Supermassive black holes are the result from the merger of stellar black holes and other matter, from the collapse of a extremely high mass star. They were formed when the Universe was still very young.

Micro black holes would be created during the collision of two very high energy particles.

How can we see Black Holes?Scientists can't see black holes. They are invisible because no light can get out. With special tools they can see where black holes are located in three different ways:

Surroundings: They can see how stars that are very close to black holes act differently than other stars. The light emitted by them will appear distorted or the stars will appear to move in an unusual way.

Gravitational effect on planets, comets and asteroids.

With the Hawking Radiation: Stephen Hawkings says that energy escape from a black hole. Matter will be created in the form of an electron and anti-electron. When it happens near the event horizon, the positive particle is ejected away from the black hole and the negative particle falls into the black hole. Therefore, black holes lose more mass than they gain.

Recent Discoveries2013/2014

*Astronomers have discovered a black hole that is consuming gas from a nearby star 10 times faster than previously thought possible. The black hole lies about 12 million light years from Earth and is ingesting a weight equivalent to 100 billion hot dogs every minute.

*Astronomers working with NASA have found a pulsating dead star beaming with the energy of about 10 million suns. The object, previously thought to be a black hole because it is so powerful, is in fact a pulsar - the incredibly dense rotating remains of a star.

*There is an ultra-compact dwarf (little) galaxy located about 55 million light-years from Earth in the Virgo cluster. Despite its diminutive stance, the galaxy appears to harbor a supermassive black hole.

*New evidence has been uncovered for the presence of a jet of high-energy particles blasting out of the Milky Way's supermassive black hole. Astronomers have made the best case ever that a jet exists by combining X-ray data from NASA's Chandra X-ray Observatory with radio emission from the NSF's Very Large Array (VLA).

Could the Earth be destroyed by a Black Hole?

No Black Hole isclose enough to the solar system for Earthto be destroyed by it.

If a Black Hole of the same mass took the place of the sun, Earth wouldn't fall in, because the Black hole would have the same gravity as the sun and our planet would orbit the Black Hole, as would the rest of planets.

Other things would be affected, such as the amount of light.

Stephen Hawkings talks about Black Holes

In the “Festival Starmus” in Tenerife, Stephen Hawkings said that there is an exit in black holes. Particles can get out of them by returning outside or arriving to another universe.

He also said that if a particle falls into a black hole, its partner can follow it or not. In the second case, this is what origins the radiation emitted from black holes, called Hawking Radiation as we talked about. He added that when the anti-particle falls into a black hole is possible that it is travelling to the past and that it can lose information.

Here there is a video of Black Holes

http://www.space.com/15421-black-holes-facts-formation-discovery-sdcmp.html

Thanks for listening...