What are black holes? by Andrea Ponce

Recently we have done an assignment on itslearning about stellar evolution and black holes. Black holes are a place where an object's gravitational pull is very strong because a much larger object has been compressed very small in comparison. Here the gravitational pull is very strong that the only things which would escape it's grip would be something with a speed greater than light which is impossible, at least so far to our knowledge. In a black hole there is a singularity, an event horizon, an accretion disk, and a jet. The singularity is at the center of the black hole, there at its center there is an infinite density but a volume of zero, at the singularity the laws of physics break. The event horizon is what surrounds the black hole in a way the black holes edge. There is where light disappears, nothing can be seen and nothing can escape, it is known as the point of no escape. The acceleration disk is where bright matter being sucked into the black hole surrounds it. It "feeds" the black hole but is dimmed when there is nothing left to "feed" the black hole with. The jet/jets are produced from the black hole and are powered by the energy of the spinning black hole and interactions with the acceretion disk.

http://astronomyonline.org/OurGalaxy/Images/AlexNervosa/Diagram.gif

https://www.youtube.com/watch?v=jbb-qu0_-Xw

Space time is a measure of change that would happen over a period of time in space. It puts two concepts together in one continuum, "something that is continuous and the same throughout it is usually thought to be a series of elements or values which are only different by small small amounts". It is putting together our knowledge of the three dimensions, height, width, and depth with time in a mathematical model.

http://upload.wikimedia.org/wikipedia/commons/9/9a/World_line.png

http://www.youtube.com/watch?v=LDvfKdCjjB0

In class we did as I said an activity in which we saw through a simulation how stellar black holes are formed. This is when a star falls on itself at the end of its life. This happens to suns much larger than ours when they stop being able to have enough energy to use fusion to keep from letting the gravity compress it and turn into a red giant then a supernova. See when it turns into a Red giant we learned that even though on the outside the appearance is greater than before that on the inside gravity starts to do its magic and starts compressing the core making it hotter and denser stopping gravity's force for a short while. The star has then nothing left to use for fusion so that its temperature rises crushing all the atoms left together. 

the repulsive force that is happening between the nuclei is overcome by gravity so the core first compresses then falls back under pressure and a shock wave is processed. Material is heated and fusion makes new elements which get exploded out into space, these being the supernova. Not even the neutrons of the old star remain.

http://www.seasky.org/celestial-objects/assets/images/starlife.jpg

http://www.youtube.com/watch?v=GsvRrlDzzwM

The black hole in the center of our galaxy is a super massive black hole. It is known as an area named Sagittarius A. Its radius is 6.25 light hours or a little less but it contains 3.7 million solar masses. Some evidence for this is center stars which seem to be orbiting around nothing. Which according to the rules of science cannot happen it has to be something large with a heavy gravitational pull. The object that they seem to be circling would be too small to contain that much of gravitational pull if it wasn't a black hole considering it itself is not pulled by anything. Also radio waves have been found projected/ released from that area.

http://scienceblogs.com/startswithabang/files/2012/05/Black_Hole_Milkyway.jpeg

Links:

http://www.nasa.gov/audience/forstudents/k-4/stories/what-is-a-black-hole-k4.html

http://astronomyonline.org/OurGalaxy/Images/AlexNervosa/Diagram.gif

http://essayweb.net/astronomy/images/black_hole_large.jpg

http://curiosity.discovery.com/question/what-is-space-time

http://www.wordcentral.com/cgi-bin/student?book=Student&va=%20continuum

http://upload.wikimedia.org/wikipedia/commons/9/9a/World_line.png

http://imagine.gsfc.nasa.gov/docs/science/know_l1/supernovae.html

http://ww2.valdosta.edu/~cbarnbau/astro_demos/stellar_evol/evol_2.html

http://www.seasky.org/celestial-objects/assets/images/starlife.jpg

http://phys.org/news/2012-01-black-hole-jets.html

http://en.wikipedia.org/wiki/Polar_jet

http://www.physicsoftheuniverse.com/topics_blackholes_singularities.html

http://www.environmentalgraffiti.com/sciencetech/supermassive-black-hole-milky-way/6671

http://www.nbcnews.com/id/46968468/ns/technology_and_science-space/t/scientists-closing-black-hole-center-milky-way/#.UZ84erWTh-0

http://amazing-space.stsci.edu/resources/explorations/blackholes/lesson/whatisit/types.html