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Black holes
 

Black holes

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    Black holes Black holes Presentation Transcript

    • A black hole is a place in space where gravity pulls so muchthat even light can not get out. The gravity is so strongbecause matter has been squeezed into a tiny space. This canhappen when a star is dying.Because no light can get out, people cant see black holes.They are invisible. Space telescopes with special tools canhelp find black holes. The special tools can see how starsthat are very close to black holes act differently than otherstars. 
    • Black holes can be big or small. Scientists think the smallest black holes are as small as just one atom. These black holes are very tiny but have the mass of a large mountain. Mass is the amount of matter, or "stuff," in an object.  The largest black holes are called "supermassive." These black holes have masses that are more than 1 million suns together. Scientists have found proof that every large galaxy contains a supermassive black hole at its center. The supermassive black hole at the center of the Milky Way galaxy is called Sagittarius A. It has a mass equal to about 4 million suns and would fit inside a very large ball that could hold a few million Earths. 
    • Scientists think the smallest black holes formed when the universe began. Stellar black holes are made when the center of a very big star falls in upon itself, or collapses. When this happens, it causes a supernova. A supernova is an exploding star that blasts part of the star into space. Scientists think supermassive black holes were made at the same time as the galaxy they are in. 
    • A black hole can not be seen because strong gravity pulls all ofthe light into the middle of the black hole. But scientists can seehow the strong gravity affects the stars and gas around the blackhole. Scientists can study stars to find out if they are flyingaround, or orbiting, a black hole.When a black hole and a star are close together, high-energy lightis made. This kind of light can not be seen with human eyes.Scientists use satellites and telescopes in space to see the high-energy light.
    • Black holes do not go around in space eating stars, moons andplanets. Earth will not fall into a black hole because no black holeis close enough to the solar system for Earth to do that.Even if a black hole the same mass as the sun were to take theplace of the sun, Earth still would not fall in. The black hole wouldhave the same gravity as the sun. Earth and the other planetswould orbit the black hole as they orbit the sun now. The sun willnever turn into a black hole. The sun is not a big enough star tomake a black hole. 
    • NASA is using satellitesand telescopes that aretraveling in space to learnmore about black holes.These spacecraft helpscientists answerquestions about theuniverse.
    • As black hole facts go, this is basic one. A black hole is aplace where the gravity well is so great that a gravitationaltime dilation has occurred. This causes time to stop. Thiscauses an event horizon into which objects can fall or bepulled, but those objects will never reappear. That is the basicdefinition according to Einstein’s theory of general relativity.
    • There is no limit to how small or how large a black hole can be.The size and mass of a black hole are directly related. The moremassive a black hole is, the more space it takes up. In fact,the Schwarzschild radius ( the radius of the event horizon of ablack hole) and the mass are directly proportional to one another.Therefore, if one black hole weighs ten times as much asanother, its radius is ten times as large. For example, a black holewith a mass equal to that of our Sun would have a radius of 3kilometers, a typical 10-solar-mass black hole would have aradius of 30 kilometers, and so on.
    • The nearest black hole is1,600 light years away.That is about 16quadrillion kilometersfor Earth.
    • One the interesting black hole facts is that they can not suckup all of the matter in the Universe. Each black hole has itsown event horizon, much like the gravitational field of aplanet. If matter is not in that horizon it will never get suckedinto the black hole.
    • This one tips the scales on the heavy end as black hole factsgo: there is a super massive black hole at the center of theMilky Way galaxy. It weighs in at about 4 million solarmasses. Luckily, there is no reason to worry. This giant suckeris over 30,000 light years away.
    • Many theorists believe that a black hole can eventuallyevaporate. How is that? Steven Hawking proposed thatblack holes were not entirely black. They emit radiation.The energy that produces the radiation comes from themass of the black hole. As the radiation is emitted, theblack hole loses mass. The black hole emits more radiationthe smaller it gets. In effect, a black hole evaporates morequickly as it shrinks.