Experimental Evidence of Black Holes
By Michael Chilton

What is a black hole?
A black hole occurs when a supermassive object (like a star) is compressed by gravity into an extremely small space. This combination produces a strong gravitational field that sucks in everything nearby, even light

How would a person ever find such a dark spot in a dark night sky?
While black holes are not currently able to be observed directly, there is evidence of how they should act that can be used to indirectly observe a black hole

-General Relativity

· Karl Schwarzschild first discovered the modern idea of the black hole as a possible solution to Einstein’s Theory of General Relativity.


· As matter falls towards the hole it releases energy
· This energy excites iron atoms in the accretion disc the characteristic swirl of the black hole
· These iron atoms then emit X-rays of a special frequency called the iron line emission
· These unique X-rays can be used to determine the possibility of a black hole

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-Hawking Radiation

· Currently not observable with present-day instruments
· Hawking radiation consists of photons, neutrinos, and some other particles
· Hawking explained with quantum mechanics that black holes do actually radiate out some energy instead of sucking it all in, and this energy is Hawking radiation
· The amount of Hawking radiation produced by a black hole is so small compared to the other energy in the area it is completely overpowered by the energy released by atoms spiraling down the black hole, making it undetectable with current instruments

Why is this important?

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Experimental evidence of black holes is important because it can help to explain important parts of the Universe. It has been theorized that the galactic cores of many galaxies are actually supermassive black holes around which the entire galaxy spins. Scientists used past experimental evidence and techniques to come up with the idea that the galactic center is a black hole.

Important People

· John Michell and Pierre LaPlace first discovered the idea of the “dark star,” something with an escape velocity that not even light could match
· Karl Schwarzschild uses General Relativity to propose the modern idea of the black hole
· John Wheeler coined the term “black hole”
· Stephen Hawking proposes that black holes emit Hawking radiation