Are violet holes possible?

Leovinus · Dec 8, 2004

With black holes no light escapes. If you took mass away from a black hole bit by bit, would there be some point where high energy light cold get out -- for example, the violet part of the spectrum and higher? Would such an object therefore be considerd a violet hole? Or is it all or nothing with these things: If any light can get out, then all light can get out? <div class="Discussion_UserSignature"> </div>

thechemist · Dec 8, 2004

I think it's all or nothing. Even if something could escape, this would be far more energetic than visible-light photons, like X-rays for example. <div class="Discussion_UserSignature"> I feel better than James Brown. </div>

qzzq · Dec 8, 2004

A photon can be any color in the spectrum and it would still travel at c. Color is just an expression of its frequency, not its velocity. So your last sentence is accurate. <div class="Discussion_UserSignature"> *** </div>

Saiph · Dec 8, 2004

you can get, however, stars that the light getting away is more red than their temperature indicates. Gravitational redshifting means that all the light that gets out, is turned red as it loses energy by traveling "uphill". So a neutron star that should be very, very blue, may instead look more yellowish. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

centsworth_II · Dec 9, 2004

I know there are blue stars, so maybe there are violet stars. But they would be stars, not "holes". <div class="Discussion_UserSignature"> </div>

Leovinus · Dec 9, 2004

My thought was that there was some intermediate state or continuous range of states. I mean, there must be a minimum size for a black hole. Take away one electron and it's not a black hole. What is it then? <div class="Discussion_UserSignature"> </div>

qzzq · Dec 9, 2004

Theoretically a black hole's event horizon could be as big as a galaxy, but it's highly unlikely. Let's take our own Milky Way Galaxy. It's diameter is 100,000 lightyears, so its radius is 50,000 lightyears, which will be the radius of the event horizon of our theoretical black hole. The relation between the radius of an event horizon and the mass of a black hole is expressed through this formula: R=G (2M/c^2) R is the Schwarzschild Radius (event horizon) G is the gravitational constant (6.67e-11) M is the mass of the black hole c is the speed of light (3e8). R is 50,000 lightyears is (9.461e15 times 50,000) 473026400000000000000 meters (!). R=G (2M/c^2) --- />M=Rc^2/2G M= 473026400000000000000 . 90000000000000000 / 0,0000000001334 = 3.19e47 kg!!!! <img src="/images/icons/smile.gif" /> How big is that? Our Sun weighs 2.99e30 kg, so you'd (roughly) need 106688963210702341 stellar masses to make a black hole this massive! Arguably, there are enough stars in the Universe to create a black hole this size, but you'd need to merge an awful lot of galaxies to get one ( about 1,000,000 Milky Way Galaxies )... <div class="Discussion_UserSignature"> *** </div>

qzzq · Dec 9, 2004

Leo, When a star runs out of nuclear fuel, it starts to shed large amounts of matter, as will happen to our Sun in about 5 billion years. What's important is the core that remains, which will cool and contract into a white dwarf star; if that core has a mass of 1.4 solar masses it will collapse into a neutron star. Before that the force of the electrons is sufficient to counter the gravitational force. Taking away an electron will only speed up the process. <div class="Discussion_UserSignature"> *** </div>

Leovinus · Dec 9, 2004

Forget the electron! It was an example! But I guess there isn't a minimum mass for a black hole -- instead there is a minimum density. How does that sound? <div class="Discussion_UserSignature"> </div>

Saiph · Dec 9, 2004

not necessarily. GR predicts a disk shaped singularity for smoothly formed, rotating black holes, and while it may be 2-d (not sure) it certainly has an area, thus the bh has a finite surface density. Also, a non-smoothly formed BH (i.e. reality) will have a "chaotic" singularity, basically a big shiftng blob (big compared to a geometrical point) thay may have a volume (partially due to heisenberg) <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

Leovinus · Dec 9, 2004

But for my supposed "violet hole", the density would *not* be infinite. I'm was trying to theorize about a very dense object that is 25 cents shy of being a black hole. <div class="Discussion_UserSignature"> </div>

centsworth_II · Dec 9, 2004

I read a post recently where someone imagined a black hole loosing mass through evaporation. At a certain point, the poster reasoned that the "hole" would no longer have the mass required to maintain its state and "pop" out into space as a visible object. On the surface, this seems reasonable, but it was pointed out that 'once a black hole, always a black hole'. And there is no limit on the size of a black hole. It's not only mass, but pressure that can create a black hole. And its thought that at the creation of the universe, pressures existed that created untold numbers of subatomic-sized black holes. So I guess that large black holes, if they shrink, become small black holes, then microscopic black holes. No popping out as a visable object, no gradual releasing of light. I thought that when the shrinking black hole reached a critical size it was supposed to explode in a shower of energy, but then there's this: "It turns out that the rate of radiation increases as the mass decreases, so the black hole continues to radiate more and more intensely and to shrink more and more rapidly until it presumably vanishes entirely. "Actually, nobody is really sure what happens at the last stages of black hole evaporation: some researchers think that a tiny, stable remnant is left behind. Our current theories simply aren't good enough to let us tell for sure one way or the other." From THIS web site. <div class="Discussion_UserSignature"> </div>

Leovinus · Dec 9, 2004

Now that's interesting. The web page said that light can orbit a quark star. I wonder if photons all have to travel the same direction like rings of Saturn or could they go in any direction to form a photon cloud around the star? <div class="Discussion_UserSignature"> </div>

robnissen · Dec 9, 2004

"Once an object has become a black hole, its going to stay a black hole evan if its gets lighter. All that will happen is the event horizon will pull in until its equal in radius to the singularity." That statement is true for a "mature" black hole, but not necessarily for a "newborn" black hole. In a "mature" black hole, most of the hole is void as the mass concentrates into a singularity at the center. But at the birth of a black hole, the mass necessary to make a black hole of a given radius is going to be distributed fairly evenly across the entire diameter of the black hole. If somehow enough mass could be instantly removed from the black hole, the remaining mass would not be enough to continue to contract (for the reasons that a quark star can't contract into a black hole), and the black hole should reappear as a quark star. But again this would only be possible (assuming that somehow mass could be taken out of the black hole) for a very "short time" after the black hole formed. Because once the mass of the black hole gets sufficiently contracted, taking mass out would only make the radius of the black hole smaller. BTW, I have no idea if a "short time" is nanoseconds, seconds, days, weeks, or months, because I have no idea how quickly mass collapses into a singurality once the event horizon is created in a newborn black hole.

Saiph · Dec 9, 2004

black hole collapse is on the order of fractions of a second IIRC. And once the mass falls behind the event horizon shroud (that grows as the material compacts, it doesn't just appear) then there is no way for it to snap out that I know of. Heck, the momentum it'll have making it go towards the center will preclude any quantum uncertainty as well. <div class="Discussion_UserSignature"> --------------------SaiphMOD@gmail.com -------------------"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- The Tenth Doctor, "Blink" </div>

dragon04 · Dec 10, 2004

I'm a layperson. But if I understand this all correctly, once a black hole loses sufficient mass relative to its surrounding environment. it would cease to exist beyond Eintsteinian physics and resume its place in the realm of the visible and measurable. I don't believe that a black hole can be of just any arbitrary size and remain so into an infinite future. If models are correct and a black hole loses sufficient mass to not infintely warp gravity at its event horizon, it seems to me that it would resume its place as a normal object in visible space. As its gravity well becomes "space normal", I'd think that it would simply exhibit the physical characteristics of any other massive object that is comparable in our universe. It seems counterintuitive to me that a black hole could REMAIN a black hole as it "evaporates". AT some point, its mass reduction should bring it back into normal space time. <div class="Discussion_UserSignature"> "2012.. Year of the Dragon!! Get on the Dragon Wagon!". </div>

nexium · Dec 10, 2004

An almost blackhole would be a quark star, if there are any. The gamma rays have trillions of times more energy than the radio waves, so perhaps the lower energy photons would not escape the almost event horizon and the gamma would be gravity red shifted to infrared and radio waves as it escapes a quark star. I'm guessing, so please refute or embellish. Neil

Are violet holes possible?

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