Author Topic: Planetary formation around Black Hole accretion disks  (Read 2519 times)

Offline darkfizzikcowboy

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Planetary formation around Black Hole accretion disks
« on: May 02, 2013, 03:48:02 PM »
Been thinking about this one for a while now especially since I've been listing to the Titanium Physicists podcast. Could a planet or even a dwarf planet form in a Black Hole's accretion disk or would the gravitational forces be prohibitive to such formation? Love the show and I've listened to all of them ( ok i'm halfway through episode 30 ). I really love how you and the physicists take a complex subject boil it down to simple concepts without losing the concept. I know its difficult since I had to research paper on a comparison of the geologic similarities between Mercury and our Moon. 
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Offline scikopas

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Re: Planetary formation around Black Hole accretion disks
« Reply #1 on: May 02, 2013, 10:32:47 PM »
The way I understand it (take what I say with a grain of salt--I'm not an astrophysicist), planetary formation happens in the accretion disc around stars, but not generally around a black hole. I expect that the particle density and temperature in the accretion disc around a black hole is too high for much to form without being torn apart by so many other particles around it...

but at the same time, where is the limit of the accretion disc?  If the whole Milky Way is in a plane around Sagittarius A* (the big black hole at the middle of our galaxy), then does that make most of our galaxy part of the accretion disc of this black hole?
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Offline CthulhuKid

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Re: Planetary formation around Black Hole accretion disks
« Reply #2 on: May 03, 2013, 08:26:48 AM »
I would imagine they wouldn't have time to before they crossed the event horizon.  There might be a "clump" of matter forming, but at those speeds, sticking everything together would be difficult.

Maybe if we pictured the disk as a plane filled with bees.....

Offline darkfizzikcowboy

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Re: Planetary formation around Black Hole accretion disks
« Reply #3 on: May 03, 2013, 12:24:40 PM »
I'm sure that the temperature would be a hurdle to formation. Actually that might be primary formation inhibitor. I do agree if any formation did occur it would be a very short lived object  in the grand scheme in the universe but it would be an interesting find it it happen
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Offline bn

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Re: Planetary formation around Black Hole accretion disks
« Reply #4 on: May 04, 2013, 03:08:57 AM »
hmmm. I don't see why not. I'll ask dave. HEY DAVE!
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Offline Grawk1

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Re: Planetary formation around Black Hole accretion disks
« Reply #5 on: June 27, 2013, 09:35:46 AM »
Related question: why is there such a significant average angular momentum as to create an accretion disk moving in one direction?Shouldn't the average angular momentum be zero? Do black hole accretion disks spin in different directions in different galaxies/parts of the universe?

Offline bn

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Re: Planetary formation around Black Hole accretion disks
« Reply #6 on: June 27, 2013, 10:51:26 AM »
well.
dave didn't answer. he's pretty busy though.

your question is good.
often, i'd imagine that accretion disks come from a black hole either eating the part of the star that got blown off when it suprenovaed... or that they come from eating the gas off of orbiting neighbours which have gotten too close to them. And in both of those cases, the gas would come in with some average angular momentum.
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Offline Grawk1

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Re: Planetary formation around Black Hole accretion disks
« Reply #7 on: June 27, 2013, 07:11:54 PM »
Ah, I see. I wondered whether it had something to do with the total angular momentum of the galaxy it was in. Thanks for clarifying!