Black Holes part 2

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Message 1468822 - Posted: 25 Jan 2014, 18:30:23 UTC - in response to Message 1468718.  

Probably mentioned it before (maybe even in this thread... heh) but I have no idea why physicists/cosmologists don't seem to consider GR time dilation in the collapse when an object nears its Schwarzchild radius/event horizon. From our perspective, it would asymptotically approach this size and never reach it, never mind collapse to a point of infinite density. Any "true" black holes inside their own event horizons would have to be primordial.

The non-primordial ones, then, could be 99.99% or whatever arbitrary closeness time permits of the way there and have all the effects that black holes are supposed to have on the space and matter around them, but could never attain that last fraction in finite time. No infinite densities thus no breakdown of physical laws to have to deal with.

No doubt the specialists know all about the subtle physics, it's just that the subtleties don't make it to the pop press.

You sometimes run into the deprecated moniker "frozen stars" in reference to black holes. That refers to just what you are talking about...from the external universe's standpoint the collapse never actually happens.

For someone falling through the event horizon it does. But for the falling observer, the external universe would speed up such that the entire future history of everything would flash by as the horizon is passed. To me that means that all the radiation (starlight, mostly) that would fall into the black hole over all the rest of time would blast the falling observer in an instant. That can't be pleasant.

That also suggests to me that once (if somehow) the observer is inside the horizon, the external universe has ended. All time has passed, and more. Or something. As I've said before I wish we had some real astrophysicists around here sometimes.
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Message 1469125 - Posted: 26 Jan 2014, 14:34:20 UTC

Prof.Hawking has proposed that black holes are really gray holes. Read this:
Gray Holes
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Message 1469319 - Posted: 26 Jan 2014, 23:18:29 UTC - in response to Message 1469125.  

Prof.Hawking has proposed that black holes are really gray holes. Read this:
Gray Holes
Tullio


Thanks Tullio, for the article.

I'm not a huge fan of Prof.Hawking. He has been proven wrong on Black Holes, before.

I remember this documentary which aired some time ago.

http://icecoldscience.blogspot.com/2011/07/hawking-paradox-aka-hawking-vs-susskind.html
The Hawking Paradox aka Hawking vs Susskind
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Message 1469412 - Posted: 27 Jan 2014, 6:26:07 UTC - in response to Message 1469319.  

I admire prof. Hawking for what he is doing despite his physical condition. A theoretical physicist who is also a far relative of mine and has fallen ill like him does nothing but crying.
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Message 1469426 - Posted: 27 Jan 2014, 7:30:30 UTC - in response to Message 1469412.  
Last modified: 27 Jan 2014, 7:32:50 UTC

I admire prof. Hawking for what he is doing despite his physical condition. A theoretical physicist who is also a far relative of mine and has fallen ill like him does nothing but crying.
Tullio



Tullio, I'm not a huge fan of Prof.Hawking. In no way did I ever or even implied about his physical condition. I'm sorry if you read my post like that. :(
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Message 1469440 - Posted: 27 Jan 2014, 8:37:33 UTC - in response to Message 1469426.  

No, I did not misread your post. You were talking about science, but I see Hawking as a suffering human being, like my brother-in-law.
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Message 1470662 - Posted: 30 Jan 2014, 7:57:52 UTC

Active supermassive black holes revealed in merging galaxies


Astronomers have conducted infrared observations of luminous, gas-rich, merging galaxies to study active, mass-accreting supermassive black holes (SMBHs). They found that at least one SMBH almost always becomes active and luminous by accreting a large amount of material


It is now believed that many galaxies have supermassive black holes at their centers, and that whether such galaxies are active galaxies is a question of whether mass is being fed into these black holes. The simplest ideas for the origin of such supermassive black holes are that they are conglomerations of many star-size black holes that were formed during the history of a galaxy, or perhaps that galaxies formed around large black holes that then grew by accreting matter.
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Message 1481878 - Posted: 26 Feb 2014, 11:37:43 UTC

Clouds seen circling supermassive black hole

Astronomers see huge clouds of gas orbiting supermassive black holes at the centres of galaxies. Once thought to be a relatively uniform, fog-like ring, the accreting matter instead forms clumps dense enough to intermittently dim the intense radiation blazing forth as these enormous objects condense and consume matter.


In 2003, scientists discovered what seemed to be a cloud of gas, termed G2, which should collide in March or thereabouts with the supermassive black hole that lurks at the heart of the Milky Way. The interaction will reveal much about this black hole.
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Message 1482898 - Posted: 28 Feb 2014, 20:15:25 UTC

Winds from Black Holes Pack Surprisingly Strong Punch

To help solve this mystery, scientists investigated the black hole called MQ1 at the center of its host galaxy, M83, for more than a year. The galaxy lies about 15 million light-years away from Earth in the constellation Hydra, and is one of the closest and brightest spiral galaxies in the sky, visible with only binoculars.

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Message 1485149 - Posted: 6 Mar 2014, 1:23:11 UTC - in response to Message 1482898.  

For the first time, astronomers have directly measured how fast a black hole spins, clocking its rotation at nearly half the speed of light.

That's fast.

http://www.space.com/24936-supermassive-black-hole-spin-quasar.html
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Message 1485732 - Posted: 7 Mar 2014, 13:12:08 UTC - in response to Message 1485149.  
Last modified: 7 Mar 2014, 13:13:21 UTC

For the first time, astronomers have directly measured how fast a black hole spins, clocking its rotation at nearly half the speed of light.

That's fast.

http://www.space.com/24936-supermassive-black-hole-spin-quasar.html

Phew... No surprise but good to see...

As well as relativistic time effects, that also adds further weird effects due to frame dragging and also for how whatever raggedy 'event horizon' is greatly distorted from that of a simple sphere...

Quite a physics headache!


Note also that for rotation to be 'seen', that also suggests that there is no such thing as a 'singularity', which also removes the surrounding impossibilities surrounding the various infinities...


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Message 1485743 - Posted: 7 Mar 2014, 14:52:26 UTC - in response to Message 1485732.  

Do you think that the center of a black hole can be any denser than a Neutron Star ?
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Message 1486180 - Posted: 8 Mar 2014, 13:52:36 UTC - in response to Message 1485743.  

Do you think that the center of a black hole can be any denser than a Neutron Star ?

The present known physics suggests that to be the case...


The question then is what new physics limits the collapse, or whether the limit is time itself.

Just for one example, there is going to be some very interesting relatavistic shear across whatever central object as it is spun up to relatavistic significant speeds. You then may well have the effects of relativity AND rotation AND... limiting further collapse...


And... It's all got to be Quantum :-)


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Message 1489640 - Posted: 16 Mar 2014, 5:26:59 UTC - in response to Message 1486180.  

maybe?

Every black hole conceals a secret — the quantum remains of the star from which it formed, say a group of scientists, who also predict that these stars can later emerge once the black hole evaporates.


Black Hole 'Information' Paradox May Have Been Resolved

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Message 1499135 - Posted: 3 Apr 2014, 15:18:32 UTC

What Stephen Hawking Really Meant When He Said There Are No Black Holes


Hawking's quip instead concerns black holes in a highly theoretical sense. Like many other theorists, Hawking has been trying to understand a paradox eating at the heart of physics. The issue—often referred to as the black hole firewall paradox—implies that physicists might have to abandon (or deeply modify) quantum mechanics or Einstein's general theory of relativity, or both.

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Message 1520020 - Posted: 22 May 2014, 22:51:44 UTC - in response to Message 1499135.  

NASA's WISE Findings Poke Hole in Black Hole 'Doughnut' Theory

A survey of more than 170,000 supermassive black holes, using NASA's Wide-field Infrared Survey Explorer (WISE), has astronomers reexamining a decades-old theory about the varying appearances of these interstellar objects.

http://www.nasa.gov/press/2014/may/nasas-wise-findings-poke-hole-in-black-hole-doughnut-theory/index.html

pic, inside link.
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Message 1520025 - Posted: 22 May 2014, 23:10:27 UTC - in response to Message 1520020.  

NASA's WISE Findings Poke Hole in Black Hole 'Doughnut' Theory

A survey of more than 170,000 supermassive black holes, using NASA's Wide-field Infrared Survey Explorer (WISE), has astronomers reexamining a decades-old theory about the varying appearances of these interstellar objects.

http://www.nasa.gov/press/2014/may/nasas-wise-findings-poke-hole-in-black-hole-doughnut-theory/index.html

pic, inside link.


Very interesting Lynn, thank you, and a pretty picture too. :) Definitely one to watch!

A quote from the article:

Another way to understand the WISE results involves dark matter. Dark matter is an invisible substance that dominates matter in the universe, outweighing the regular matter that makes up people, planets and stars. Every galaxy sits in the center of a dark matter halo. Bigger halos have more gravity and, therefore, pull other galaxies toward them.

Because WISE found that the obscured black holes are more clustered than the others, the researchers know those hidden black holes reside in galaxies with larger dark matter halos. Though the halos themselves would not be responsible for hiding the black holes, they could be a clue about what is occurring.


Intriguing :)
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Message 1532194 - Posted: 26 Jun 2014, 4:31:56 UTC

Rare trio of supermassive black holes found

Apologies if this has already been posted.
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Message 1532321 - Posted: 26 Jun 2014, 13:53:25 UTC - in response to Message 1532194.  

Rare trio of supermassive black holes found

Apologies if this has already been posted.

This story has been in the news in South Africa today, because the lead researcher is a South African from my alma mater, the University of Cape Town.
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Message 1532337 - Posted: 26 Jun 2014, 15:02:36 UTC - in response to Message 1532321.  

Rare trio of supermassive black holes found

Apologies if this has already been posted.

This story has been in the news in South Africa today, because the lead researcher is a South African from my alma mater, the University of Cape Town.


That did impress me :) of course I'm totally jealous you went to Cape Town Uni :) it was landlocked Witwatersrand for me :)
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Message boards : Science (non-SETI) : Black Holes part 2


 
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