Biggish black holes without accretion disks?

ehkzu · Feb 13, 2005

I'm working on a story for which it would be useful to have a sizeable black hole without an accretion disk or companion star, making the singularity harder to locate/identify than the normal black hole. However, I'm also committed to plausibility. So--is an accretion diskless black hole possible, even if unlikely? Or would the explosion attending the formation of a black hole always smash the dying star's orbiting planets into bits and create an accretion disk? Or even if so, if it were an older black hole, might the disk have petered out? After all, a black hole's gravitational attraction is the same as the star it once was plus whatever was spiraling into it. So something going fast enough around isn't going to fall in, yes? Related question: If a spaceship with spin gravity got near a black hole, I assume the gravity differential would strain the ship and its occupants. I realize the more massive the singularity, the fatter the affected zone outside the event horizon. I'm hoping for an effect strong enough to damage a ship's electronics before it started doing serious damage to human occupants. I'm assuming a larger black hole with a fatter "zone of effect" would allow such problems to have a more gradual onset.

newtonian · Feb 14, 2005

ehkzu - Star differs from star in glory (1 Corinthians 15:41) Stars with no set course, for whom the blackness of darkness stands reserved forever (Jude 13) The former has been being proven through continued study of an almost infinity variety of stars- some of whom become black holes. The latter could be referring to black holes which have excaped the gravity and light of our universe. Given that extreme variety, it would seem likely some black holes would have no accretion disk. A black hole in total darkness forever could not have an accretion disk, since said disk would cause light to be in the environment of the black hole. I'll let other post some of the many possible models and scenarios for black hole formation.

thalion · Feb 14, 2005

For the former question, it is IMO undoubtedly possible to have a black hole without an accretion. A black hole formed in a supernova explosion of a lone star would probably have no accretion disk at all after a few thousand years, not to mention other black holes that could be ejected from binary systems when their primary goes "boom" and loses too much mass. So, I can't say much for the second question (relativity is not my strong suit), but as for the former it looks definitely plausible. Heck, for all we know the majority of black holes in the Galaxy may be without accretion disks.

5stone10 · Feb 14, 2005

I've never read where an accretion disk is required w/ a black hole. Black holes w/o accretion disks could be identified through their escaping x-ray jets. I'm not sure the second question makes sense. I don't see how an object without approximately equivalent mass would have any gravitational effect [offset] on an approaching black hole.

ehkzu · Feb 14, 2005

Thanks. People often think scifi can be just made up. But if you want to keep down your "black box" count you have to do your homework. --Ehkzu

5stone10 · Feb 14, 2005

Here's a pretty good summary of a basic detection method from CalTech >> "Suppose you have found a region of space where you think there might be a black hole. How can you check whether there is one or not? The first thing you'd like to do is measure how much mass there is in that region. If you've found a large mass concentrated in a small volume, and if the mass is dark, then it's a good guess that there's a black hole there."

newtonian · Feb 14, 2005

5stone10- I don't think x-ray jets from black holes would be possible without accretion of matter.

Saiph · Feb 14, 2005

any tidal forces that would mess with people, would destroy the people before the electronics, merely due to the resilience of the materials concerned. Any electrical and magnetic fields would mess with the electronics first, since they are much more susceptable. Of course, mission critical devices will be very heavily shielded and designed to be robust. If you get really close, temporal effects will start to mess with things. It may bother computers more than people, at first, due to the precision timing required. If it suddenly takes longer for signals to cross a chip, everything gets outa whack. Of course, that close, and people would basically have to know there's a BH out their window. <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>

iron_sun_254 · Feb 15, 2005

Temporal effects would have no effect on the computers because until it was so close to the black hole that there was a large enough gradiant that one side of the chip was working differently than the other.

Saiph · Feb 16, 2005

right, as I said, really close. <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>

nexium · Feb 16, 2005

I agree an accretion disk is essential to the presence of a jet. Both can be negligible for any size black hole. There may be lots of black holes that are almost undetectable until you are dangerously close to the event horizon. Low mass black holes (if any exist) will have distructive tide effects= gravity differential at more than twice the event horizon radius, which may be less than an inch. In a high speed collision with such a low mass black hole, I think there will be hole clear though the ship that could remove essential components of the ship without any damage to the crew other than high radiation exposure. A very massive black hole has tiny tidle effects outside the event horizon, so damage to the crew and electronics is unlikely, unless one or both were tolarent only of microgravity. Large structures of the ship are more valnerable to tide effects = gravity differential than medium size and tiny objects are close to invalnerable. Neil

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