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Black Hole Cluster Spawns Massive Cloud
Shifty Jim writes in with an article at space.com reporting that a cluster of galaxies harboring black holes may be the source of a massive cloud millions of light years across. Quoting: "A giant cloud of superheated gas 6 million light years wide might be formed by the collective sigh of several supermassive black holes, scientists say. The plasma cloud... might be the source of mysterious cosmic rays that permeate our universe... The plasma cloud is located about 300 million light years away near the Coma Cluster and is spread across a vast region of space thought to contain several galaxies with supermassive black holes... embedded at their centers."
Google "Hawking Radiation". (Thermal radiation thought to be emitted by black holes due to quantum effects - named after British physicist Stephen Hawking, who provided the theoretical argument for its existence in 1974.)
Black holes actually do radiate - they are actually not black at all. The result is that small black holes will evaporate and disappear after a while. Bigger ones are probably indistinguishable from an ordinary star when viewed from a distance. The difference being their mass which would be disproportionate to their luminosity. Read Hawking's "A Brief History of Time" for illumination.
Excuse me, but please get off my Pennisetum Clandestinum, eh!
Actually, it's the *really* small ones(on the order of the mass of maybe half the moon, or smaller) that evaporate very quickly. The supermassive ones radiate at a very low rate and will last many, many, many billions of years. The temperature of the universe(eg: background radiation) will need to drop before they'll be "hotter" than their surroundings. Currently the big black holes are soaking up more radiation than they're emitting(hence, black)
"so what makes this guy think this particular "cloud" has agreater probability of being the source of the "cosmic rays" that "permeate" our universe?"
They don't:
"he new finding could also help explain the unwanted and confusing "noise" scientists observe in the Cosmic Microwave Background (CMB), Kronberg said. The CMB is a ubiquitous radiation in the universe that is said to be a remnant of the Big Bang."
Now, if you read that carefully, it is said that this could explain the *noise* in the CMB, not the CMB itself. Half a point for reading through the article though.
http://www.journals.uchicago.edu/ApJ/journal/issue s/ApJ/v659n1/64492/brief/64492.abstract.html
I suggest you learn a little bit of the math behind black hole evaporation.
Here I refer to Wikipedia because I'm lazy...http://en.wikipedia.org/wiki/Hawking_evapor ation#Black_hole_evaporation
You'll notice that from the Power emitted from a black hole is inversely proportional to the Mass Squared, so Big Black holes don't emit much power, making them effectively black. Not you described indistinguishable from a star when viewed from a distance.
Also the time it takes for a black hole to evaporate is proportional to the Mass cubed, so the bigger the black hole is, the longer it takes to evaporate.
Also its my understanding that these equations assume that the black hole is not feeding and gaining mass. When a black hole does so the surrounding material heats up emits x-rays. Its this x-ray signature that makes them easy to find. Super massive black holes may not have the same x-ray signature, their surroundings being black as well. Those are detected by their gravitational influence: Sagittarius A* was detected this way. (Though its not completely quiet). Still when mass is a function of time and increasing, the mass added to a black hole affects how long it will take to evaporate.
If someone is passing you on the right, you are an asshole for driving in the wrong lane.
Seriously, the parent completely misstated the intensity of hawking radiation. I can't believe it got modded up to 4 in the first place.
Now, black holes are often surrounded by bright clouds, but the clouds are bright for reasons completely unrelated to hawking radiation. As stuff falls into a black hole, it gets accelerated until it's going really fast. Once it gets fast enough, the light generated by the friction of the things falling in gets blue-shifted until it moves into the x-ray range. Now, this does occur a lot, so many black holes are detectable as the presumed center of giant x-ray vortexes, but that is completely different from hawking radiation since this is caused by material external to the black hole falling in.