English subtitles for clip: File:Shedding Light on Black Holes (NASA ScienceCasts).ogv

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Shedding Light on Black Holes – presented by Science@NASA

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"Black holes" is one of the most highly searched terms about our universe.

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There’s a fascination with the idea of a region of space having a gravitational pull so strong,

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nothing can escape its deadly grasp, not even a sliver of light.

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Well, not quite. In fact, much of what we think we know about black holes turn out to be myths.

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Myth 1 – All black holes are black. As this photograph from the Event Horizon telescope demonstrated,

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light can be detected near a black hole’s event horizon.

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This is the boundary between normal space and the space affected by the black hole's gravity,

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from which no escape is possible. Part of this light comes from the black hole’s accretion disk,

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a flat, pancake like structure composed of dust, gas and other debris.

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Friction constantly moves the disk’s material inward toward the event horizon.

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Light also comes from jet streams which propel matter outward along the disk’s north and south poles.

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Myth 2: All black holes are about the same size.

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Black holes actually come in several different sizes which are defined by their mass.

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Small black holes are usually the result of a relatively short and violent collapse of a star.

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Recent work suggests that Intermediate black holes are found in the nuclei of some active galaxies.

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Super massive black holes on the other hand, are found at the center of nearly every galaxy.

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Dr. Dan Evans, an Astrophysicist at NASA Headquarters says,

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“There’s a direct relationship between the beginning of super massive black holes

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and the beginning of their corresponding galaxy.

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This strongly suggests the two were born about the same time and slowly grew in size together over billions of years.”

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Myth 3: If you get within a few thousand miles of a black hole, its super gravity will pull you into its center.

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It turns out you can get surprisingly close to a black hole.

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If you approached a black hole with mass equal to our Sun’s for example, you could get as close as tens of miles.

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So imagine if we replaced our sun with a black hole of the same mass.

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All of the planets would continue to revolve around it, at exactly the same speed and distance as they do now.

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Myth 4: Once inside a black hole, nothing ever comes out.

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Nope. It turns out that radiation can escape from a black hole.

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One of Stephen Hawking’s contributions was a theory that a black hole is not so dense in a quantum mechanical sense.

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The slow leak of what’s now known as Hawking radiation would, over time, cause the black hole to simply evaporate.

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The image from the Event Horizon telescope confirmed

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what Albert Einstein’s general theory of relativity predicted over 100 years ago,

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that a black hole’s form is that of a perfect circle.

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And as scientists learn even more about the properties of this gigantic cosmic mystery we call a black hole,

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they’ll be able to puncture even more myths.

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To hear more true tales about black holes and other mysteries of the cosmos, visit science.nasa.gov