Galaxies
Black Holes
Astrophysics

How do black holes and galaxies project light?

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Wiki User
2009-08-30 23:43:44

Black holes do NOT project light. Hence the name black hole.

Their gravity field is so strong that nothing escapes, not even

light photons. The only way we know they exist by the bending of

the trajectory of photons passing them. Galaxies project light via

radiant energy, i.e. photons. In the same way you observe a

lightbulb, you observe a galaxy. The primary difference is that we

have developed instruments to not just observe galactic energy

within the visible spectrum, but the entire electromagnetic

spectrum, e.g. radio waves and x-rays. Those instruments would work

with a lightbulb too, but they're usually busy looking at galaxies.

Actually, black holes probably do give off light (and all other

particles). This effect is quantum mechanical in nature and was

discovered by Stephen Hawking. However, it is not at present

possible to measure this. Whether or not Hawking is right, we can

observe black holes, and not just because of light from distant

stars bending around them. The event horizon is a very violent

place, and materials are being spun around in the vortex just

outside of the horizon, and they are being torn apart before

entering the horizon as well. All of this creates a massive output

of energy that we can observe. We get hints that we are observing a

black hole by observing how nearby stars interact with it. Black

holes sometimes 'suck up' so much matter that some of it escapes.

http://www.tqnyc.org/2006/NYC063368/the_stars.htm


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