Astronomy for beginners Black Holes Aashman Vyas

What are Black Holes? A black hole is a super dense object that has an intense gravitational pull There are three parts to a black hole, a singularity, event horizon and accretion disk 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 299, km per second) Although the event horizon is part of a black hole, it is not a tangible object The singularity is not really a tangible object either According to the General Theory of Relativity the Singularity is a point of infinite space time curvature Everything that falls into a black hole by passing the event horizon, including light, will eventually reach the singularity of a black hole Before something reaches the singularity it is torn apart by intense gravitational forces (even the atoms)

How do Black Holes form? 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 keeps this star from collapsing onto itself and becoming a black hole? 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 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 sun. When the fuel that feeds the nuclear reactions gets used up the massive star cannot support itself anymore 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 cannot 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 actually impossible to watch the final steps of the formation of the black hole from a stationary external reference frame 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 stationary external reference frame 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 any object fall into a black hole 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 any object fall into 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 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 by the immense gravity near the outside of 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 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 by the immense gravity near the outside of a black hole.

Types of Black Holes There are two types of black holes There are two types of black holes -Stellar mass black holes -Supermassive black holes Stellar black holes are the black holes formed by stars that collapse Stellar black holes are the black holes formed by stars that collapse Supermassive black holes form when lots of black holes collide or when huge stars collapse. They are found only in the center of galaxies Supermassive black holes form when lots of black holes collide or when huge stars collapse. They are found only in the center of galaxies

Formation of Stellar Mass Black Holes -Star goes supernova (see stars presentation) -Too much element build up -shrinking effect (see stars presentation) -Core shrinks and crushes atoms -Creating a black hole -Supernova remnant will be it’s first snack

Formation of Supermassive Black Hole Scenario1 -Lots of stellar black holes collide producing disturbance due to colliding event horizons -A few million years later they all become one black hole -resulting black hole is huge

Formation of Supermassive Black Hole Scenario2 When the universe was young, stars were sometimes as big as a solar system When the universe was young, stars were sometimes as big as a solar system So you can image what would happen if a star as big as the solar system exploded and how long the life of that star would be…(see my stars presentation) So you can image what would happen if a star as big as the solar system exploded and how long the life of that star would be…(see my stars presentation) You can also imagine what would happen if a star that size turned into a black hole… You can also imagine what would happen if a star that size turned into a black hole… These black holes could also have played a part in the formation of galaxies These black holes could also have played a part in the formation of galaxies

Cool facts 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 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 back of your head will travel though space that is bent so much by gravity that it will enter your eyes Another cool thing about black holes is that they might be able to destroy information. The destruction of information is not allowed by quantum mechanics, so Hawking concludes that the usual rules of QQQQ uuuu aaaa nnnn tttt uuuu mmmm M M M M eeee cccc hhhh aaaa nnnn iiii cccc ssss cannot apply for black holes!! 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 energy/radiation. (E=mc2) So a black hole would radiate away all it’s mass in about…lets see….about a trillion years

Bibliography An introduction to black holes by David Ando An introduction to black holes by David Ando Ask an astronomer for kids Ask an astronomer for kids Astronomy.com Astronomy.com The big book of stars and planets by Robin Kerrod The big book of stars and planets by Robin Kerrod The elegant universe (TV show) discovery science The elegant universe (TV show) discovery science Google images Google images

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