Astronomy for beginners Astronomy for beginners

Black HolesBlack Holes

Aashman VyasAashman Vyas

What are Black Holes?What are Black Holes? A black hole is a super dense object that has an intense A black hole is a super dense object that has an intense

gravitational pullgravitational pull There are three parts to a black hole, a singularity, event horizon There are three parts to a black hole, a singularity, event horizon

and accretion diskand accretion disk The event horizon is where the force of gravity becomes so strong The event horizon is where the force of gravity becomes so strong

that even light is pulled into the black hole (light has a speed of that even light is pulled into the black hole (light has a speed of 299,792.458 km per second)299,792.458 km per second)

  Although the event horizon is part of a black hole, it is not a tangible Although the event horizon is part of a black hole, it is not a tangible object object

The singularity is not really a tangible object eitherThe singularity is not really a tangible object either According to the General Theory of Relativity the Singularity is a According to the General Theory of Relativity the Singularity is a

point of infinite space time curvaturepoint of infinite space time curvature Everything that falls into a black hole by passing the event horizon, Everything that falls into a black hole by passing the event horizon,

including light, will eventually reach the singularity of a black hole including light, will eventually reach the singularity of a black hole Before something reaches the singularity it is torn apart by intense Before something reaches the singularity it is torn apart by intense

gravitational forces (even the atoms)gravitational forces (even the atoms)

How do Black Holes form? How do Black Holes form?   Imagine a star which is much more massive than our sun, and which has a mass, Imagine a star which is much more massive than our sun, and which has a mass,

called the critical mass, which is large enough to cause a black hole to form. What called the critical mass, which is large enough to cause a black hole to form. What keeps this star from collapsing onto itself and becoming a black hole?keeps this star from collapsing onto itself and becoming a black hole?

The answer is that there is an intense pressure caused by nuclear reactions within The answer is that there is an intense pressure caused by nuclear reactions within the sun. When the fuel that feeds the nuclear reactions gets used up the massive star the sun. When the fuel that feeds the nuclear reactions gets used up the massive star cannot support itself anymorecannot support itself anymore

It then collapses to form a black hole.   It then collapses to form a black hole.    It is interesting to note that when a black hole is formed by a collapsing star it is It is interesting to note that when a black hole is formed by a collapsing star it is

actually impossible to watch the final steps of the formation of the black hole from a actually impossible to watch the final steps of the formation of the black hole from a stationary external reference framestationary external reference frame

An external reference frame is a place where one watches the formation of the black An external reference frame is a place where one watches the formation of the black hole from far away, like an astronomer on Earth. In addition, it is impossible to see hole from far away, like an astronomer on Earth. In addition, it is impossible to see any object fall into a black holeany object fall into a black hole

This is not to say that everything appears to freeze just before entering a black hole. This is not to say that everything appears to freeze just before entering a black hole. As an object falls into a black hole it gets increasingly dimmer and dimmer from the As an object falls into a black hole it gets increasingly dimmer and dimmer from the point of view of an outside observer. By the time an object gets to the edge of a black point of view of an outside observer. By the time an object gets to the edge of a black hole, it will be completely black. This effect, called a gravitational redshift, is caused hole, it will be completely black. This effect, called a gravitational redshift, is caused by the immense gravity near the outside of a black hole. by the immense gravity near the outside of a black hole. 

Types of Black HolesTypes of Black Holes

There are two types of black holesThere are two types of black holes-Stellar mass black holes -Stellar mass black holes -Supermassive black holes-Supermassive black holesStellar black holes are the black holes Stellar black holes are the black holes

formed by stars that collapseformed by stars that collapseSupermassive black holes form when lots Supermassive black holes form when lots

of black holes collide or when huge stars of black holes collide or when huge stars collapse. They are found only in the center collapse. They are found only in the center of galaxiesof galaxies

Formation of Stellar Mass Black Formation of Stellar Mass Black HolesHoles

-Star goes supernova (see stars -Star goes supernova (see stars presentation)presentation)

-Too much element build up-Too much element build up

-shrinking effect (see stars presentation)-shrinking effect (see stars presentation)

-Core shrinks and crushes atoms -Core shrinks and crushes atoms

-Creating a black hole-Creating a black hole

-Supernova remnant will be it’s first snack-Supernova remnant will be it’s first snack

Formation of Supermassive Black Formation of Supermassive Black HoleHoleScenario1 Scenario1

-Lots of stellar black holes collide producing -Lots of stellar black holes collide producing disturbance due to colliding event horizons disturbance due to colliding event horizons

-A few million years later they all become -A few million years later they all become one black holeone black hole

-resulting black hole is huge-resulting black hole is huge

Formation of Supermassive Black Formation of Supermassive Black HoleHoleScenario2Scenario2

When the universe was young, stars were When the universe was young, stars were sometimes as big as a solar systemsometimes as big as a solar system

So you can image what would happen if a star So you can image what would happen if a star as big as the solar system exploded and how as big as the solar system exploded and how long the life of that star would be…(see my stars long the life of that star would be…(see my stars presentation)presentation)

You can also imagine what would happen if a You can also imagine what would happen if a star star that that size turned into a black hole…size turned into a black hole…

These black holes could also have played a part These black holes could also have played a part in the formation of galaxies in the formation of galaxies

Cool factsCool facts   First of all, if you get close enough to a black hole you will see the First of all, if you get close enough to a black hole you will see the

back of your own head! This effect, called an Einstein ring, is back of your own head! This effect, called an Einstein ring, is caused by the intense gravity around a black hole. When you are caused by the intense gravity around a black hole. When you are near a black hole at certain distances the light that leaves from the near a black hole at certain distances the light that leaves from the back of your head will travel though space that is bent so much by back of your head will travel though space that is bent so much by gravity that it will enter your eyes gravity that it will enter your eyes 

    Another cool thing about black holes is that they might be able to Another cool thing about black holes is that they might be able to destroy information. The destruction of information is not allowed by destroy information. The destruction of information is not allowed by quantum mechanics, so Hawking concludes that the usual rules of quantum mechanics, so Hawking concludes that the usual rules of Quantum MechanicsQuantum Mechanics cannot apply for black holes!! cannot apply for black holes!!

Black Holes do not last forever. In Stephen Hawking’s theory about Black Holes do not last forever. In Stephen Hawking’s theory about Black Holes, it says that black holes radiate mass in the form of Black Holes, it says that black holes radiate mass in the form of energy/radiation. (E=mc2) So a black hole would radiate away all it’s energy/radiation. (E=mc2) So a black hole would radiate away all it’s mass in about…lets see….about a trillion yearsmass in about…lets see….about a trillion years

Bibliography Bibliography

An introduction to black holes by David An introduction to black holes by David Ando Ando

Ask an astronomer for kidsAsk an astronomer for kidsAstronomy.comAstronomy.comThe big book of stars and planets by The big book of stars and planets by

Robin Kerrod Robin Kerrod The elegant universe (TV show) discovery The elegant universe (TV show) discovery

sciencescienceGoogle imagesGoogle images

Thank You For Watching!!!!