Transcript of Plus Time: Black Holes
BLACK HOLES By: Kara Reardon Discovery of Black Holes Black holes can't technically be discovered because we cannot directly see them. The closest black hole to Earth is Cygnus X-1 and it's about 8,000 light years away. There are 14 known black holes. When a star collapses it starts to form a black hole and the star gets smaller until it stops shrinking. That is the reason a black hole's original name was a frozen star, because it froze in size. Black holes have their name now because they pull in everything, including light, and nothing can escape. Black Holes' Physical Characteristics How a Black Hole is formed They form when stars bigger than the sun have a supernova explosion. The remnant of the star collapses in on itself until it shrinks to a concentrated mass with a super strong gravitational pull, creating a black hole. Why Only Large Stars Turn Into Black Holes In theory, anything could turn into a black hole if it could squeeze to a volume of zero and have an infinite density. But only large stars' cores can create a gravitational force that strong. What a Black Hole Looks Like It looks like a small black ball in space. The edge of the ball is the event horizon and the center is the singularity. The singuarity is where everything disappears from our universe. The space between the horizon and the singularity is the Schwarzchild Radius. Physics of a Black Hole One Big Theory We can't see black holes because light can't escape their horizon. We know they are there through indirect evidence, and the first sign would be that there is a HUGE amount of mass in a TINY space. They are usually located in the centers of galaxies, postulates, and quasars. There is not yet complete proof that black holes exist. Mass of a Black Hole The mass of a black hole could be millions or billions times the sun's mass. The mass of a black hole is measured by the gravity it has on stars and other things around it. Scientists and astronomers can't see the inside of a black hole because the view is blocked by millions of stars. Instead the inside of a black hole is detected through X-rays in the form of radio waves. How We Know What's on the Inside of a Black Hole Quasars At first astronomers thought that quasars were just stars, except they gave off radio waves. However, in 1963 astronomers found out that they are actually over one billion light years away. More "stars" like these were found without radio waves. Quasars are actually galaxies so far away that they normally wouldn't be seen, but their centers are so bright. It could possibly be the concentration of the light from the matter being drawn into a black hole that makes quasars so bright. The Mystery of Quasars Humans vs. Black Holes Entering a Black Hole If you entered a black hole you would experience "tidal" gravitational forces. The part of your body that is closest to the black hole would start to feel heavier than the rest of your body. You would then feel stretched and you would be stretched to the point of death. What Someone Would See as They Watched You Enter a Black Hole As you get closer to the horizon the light with you takes longer to get to someone watching you. The light would hover at the horizon and never reach the person watching you. Parts of a Black Hole Horizon of a Black Hole One way to look at the horizon of a black hole is that time passes by more slowly closer to the horizon. If you were to hover over the horizon while someone hovered farther away you would age more slowly than they would because time slows down. Schwarzchild Radius To be "sucked" into a black hole you would have to pass through the Schwarzchild Radius. This is the radius at which a gravitationally collapsing celestial body becomes a black hole. At this radius the escape speed is equal to light. When light passes through even it can't escape. Singularity The singularity is the center of the black hole and the point where the laws of physics break down. This is the point where space and time seem to disappear. The Suction of a Black Hole As black holes age, they suck in more matter from space. As they do this they also gain more mass. Aging Why the Whole Universe isn't Sucked into a Black Hole Black holes have a strong gravity force but they only suck in what crosses their horizon. And matter is slowly drawn closer to the horizon. Black Holes vs. Black Holes A black hole could suck up another black hole but it would have to be a larger one sucking up a smaller one. Black holes could also merge forming one big black hole. Both of these are rare but they have occurred. Who "Discovered" Black Holes? Karl Jansky was the first to notice something was weird in the center of our galaxy. He did this by monitoring radio waves. The radio signals that weren't normal were coming from the center of our galaxy, the Milky Way, in the constellation Sagittarius. Alyona. "Immense Universe: Quasar." Internet: <http://my.opera.com/ShizukiYUI/blog/2010/08/02/quasar> February 11, 2012.Full transcript
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