This document discusses black holes, including their definition, structure, theories of formation, methods of detection, and two specific black holes - Sagittarius A* and Cygnus X-1. It defines a black hole as a region with gravitational fields too strong for light or matter to escape, and describes their key structures like the singularity, event horizon, and accretion disk. It also outlines some theoretical explanations for black holes and how astronomers detect their effects through light deflection and influences on nearby objects.

1. BLACK
HOLES Raúl Díaz Gómez
Daniel Hirsch Marina
Carlos Ruiz Aquino
4º ESO A

2. Definition
A black hole is a region
of spacetime whose gravitational fields are too
strong for light and any mass known to escape.
Black holes don’t emit radiaton and light but the
objects they absorb do, thats why we can see
are shiny.

3. Structure of Black Holes
• The Singularity: This is the region of the black hole where all the
mass of the black hole has been compressed down to nearly zero
volume. As a result the singularity has almost infinite density and
creates an enormous gravitational force.
• The Event Horizon: This is the "point of no return". Any object,
even light, that is within this radius cannot escape the
gravitational pull of the black hole
• The Schwarzschild Radius: This is the event horizon's radius. It
is the radius at which the escape velocity is equal to the speed of
light,
R = 2GM/c2

4. Structure of Black Holes
• The Accretion Disk: This is a
disk composed of stellar
material that is spiraling
towards that black hole
• The Ergosphere: If the black
hole is rotating, then as it
spins, its mass causes the
space time around the black
hole to rotate as well. This
region is called the
ergosphere.
• 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.

5. Theories
Most things known about black holes are only theories
that are not true:
• The Einstein-Rosen Bridge Theory-> it says
that if a human goes through a black hole, he
will be suck down in a tunnel and shot out in a
“white hole” in a parallel universe.
• Collapsed stars-> it says that black holes is
simply a massive, dead star whose gravity is so
intense that even light cannot escape.

6. •Russian Dolls Universe Theory-> It says that the Universe is
an infinite dark void with infinite number of planets, stars,
galaxies and intergalactic spaces floating inside and governed by
the same physical laws and constants. Like part of a cosmic
Russian doll, our universe may be nested inside a black
hole that is itself part of a larger universe.
•How black holes are created-> A common type of black
hole is produced by certain dying stars. A star with a mass
greater than about 20 times the mass of our Sun may produce a
black hole at the end of its life. But most of the stars cannot
become a black hole because they don’t have the mass to
become it so when they die, they become white dwarf star which
will sink due to its own weight.

7. How to detect Black Holes
The black holes don’t emit electromagnetic
radiaton so it’s quite difficult to detect their
effects. His gravitatory effects can be noticed in
near objects which movement is influenced by
the black holes.
According to the relative theory, the light is
deflected when it passes near a massive object.

8. Sagitario A
It is the closest black hole to the Earth. Astronomers are confident that
these observations of Sagittarius A* provide good evidence that our own
Milky Way galaxy has a supermassive black hole at its center.
In Chile, they show how the cloud is so hot that her front has already
passed the point of maximum approach and away from the black hole of
more than ten million miles per hour, while the tail is still falling towards
him.

9. Sagitario A
Location
It is located at the center of the
Milky Way.
Discovery
It was discovered on February 13th
1974 by the astronomers Bruce
Ballick and Robert Brown using
the interferometer of the National
Radio Astronomy Observatory.

10. Cygnus X-1
It is a well-known galactic X-ray source and black hole candidate in
the constellation Cygnus. Cygnus X-1 was the first and brightest source
of x-rays discovered in Cygnus galaxy (X-rays are photons (particles
of light) that carry more energy than the light we see). It is now
estimated to have a mass about 14.8 times the mass of the Sun and has been
shown that is too compact to be any known kind of normal star or other likely
object besides a black hole. If so, the radius of its event horizon is about 44 km.

11. Cygnus X-1
Location
It is located in the Cygnus Galaxy.
Discovery
It was discovered by the Uhuru satellite in
1791.