Black holes may not exist after all::

http://phys.org/news/2014-09-black-holes.html

News at 11 I guess.

Originally posted by sonhouse
http://phys.org/news/2014-09-black-holes.html

News at 11 I guess.

I'm not buying. What are all those objects we have identified that are too compact and massive to be anything other than a black hole?

the link mentions;

"..The paper, which was recently submitted to ArXiv, an online repository of physics papers that is not peer-reviewed,.."

So, I wonder, has it been peer-reviewed at all?

But, on the other hand, it says "..was done in collaboration with Harald Peiffer, an expert on numerical relativity..."

So I assume that at least one real expert has seen it and agrees that it is sound.

But, what does a very massive collapsing star that doesn't collapse into a neutron star actually turn into if not a black hole?
And what causes the observed gravitational lensing from the said black holes if they are not really black holes?
And what is causing the massively luminous jets of matter from quasars if not feeding super massive black holes?
These basic observations appear to logically contradict the link to me.

Better tell these guys.

http://www.forbes.com/sites/alexknapp/2014/09/18/astronomers-find-a-supermassive-black-hole-in-a-tiny-galaxy/

Originally posted by wolfgang59
Better tell these guys.

http://www.forbes.com/sites/alexknapp/2014/09/18/astronomers-find-a-supermassive-black-hole-in-a-tiny-galaxy/

yes, we already knew that. But, IF we are to believe the OP link (a very big IF! ) , then that said black hole, just like all other said black holes including the one detected in the center of our own galaxy, isn't really a black hole but rather merely a very massive object (which would then beg the obvious question of what kind of very massive object it is if not a black hole? )

IF I were a betting man then I would be prepared to bet a considerable sum that this is junk.

... She and Hawking both agree that as a star collapses under its own gravity, it produces Hawking radiation. However, in her new work, Mersini-Houghton shows that by giving off this radiation, the star also sheds mass. So much so that as it shrinks it no longer has the density to become a black hole.

Before a black hole can form, the dying star swells one last time and then explodes. A singularity never forms and neither does an event horizon. The take home message of her work is clear: there is no such thing as a black hole. ...

Hawking radiation is emitted FROM an event horizon.
If there is no event horizon then there is no Hawking radiation.

So this article is talking nonsense.

EDIT: Hawking radiation increases the smaller the black hole and thus the greater the gravitational gradient.
A black hole with a couple of solar masses has a 'temperature' much lower than the cosmic background radiation [CBR]
of appx 3K. which means that at present they will net-gain mass/energy from the CBR and thus will grow untill the
CBR drops below their temperature [even without any other mass/energy sources around].

As the core collapses the gravitational sheer increases until an event horizon is formed.
Thus any 'hawking radiation' emitted during collapse would be less than that emitted once the black hole is formed.
So less than, 'much less than the cosmic background radiation'.

Also, I can't find any reference to anyone [let alone Steven Hawking] saying that hawking radiation is emitted
from anything other than an event horizon.
Also the line "She and Hawking both agree.." makes me suspicious.... Who cares if some famous person agrees with
you. The work stands on it's own, or it doesn't. Hawking's been wrong [many times] before.

Also, and this is the biggest problem I have.

Observation and facts BEFORE theory. We can observe unmistakably black holy things.
Thus if your 'maths' says they can't exist then there is something wrong with your maths.

http://www.universetoday.com/114802/there-are-no-such-things-as-black-holes/

https://briankoberlein.com/2014/09/25/yes-virginia-black-holes/

Originally posted by googlefudge
IF I were a betting man then I would be prepared to bet a considerable sum that this is junk.

[quote]... She and Hawking both agree that as a star collapses under its own gravity, [b]it produces Hawking radiation. However, in her new work, Mersini-Houghton shows that by giving off this radiation, the star also sheds mass. So much so that as it shr ...[text shortened]... o-such-things-as-black-holes/

https://briankoberlein.com/2014/09/25/yes-virginia-black-holes/[/b]

I had a very quick look at the paper and it looks reasonable enough. It's enough that there is a very strong gravitational field for Hawking radiation to be emitted. In Hawking's model it is produced near an event horizon, not from it - a positive energy particle is emitted and the negative energy particle falls through the horizon. In her model it just eats the stuff at the surface of the star. She did this work as a visitor at DAMTP and had people like Richard Ellis to talk to who'd have told her she was wrong if there was a problem as simple as that.

In her model the star gets within an inch of forming a black hole. Let's call her star a collapsar to avoid confusion. The Schwartzschild metric tells us that an observer who is near the Schartzschild radius of a collapsar has a clock running very slowly compared with an asymptotic observer. This means that someone far away from the collapsar will think a black hole has formed, what is an explosion for the observer near the surface of the collapsar will look like a black hole slowly undergoing quantum evaporation to an asymptotic observer.

A possible difficulty is that there is an object in the centre of our galaxy with a mass of millions of solar masses compressed within a radius of no more than that of the orbit of Uranus. This must have been created either primordially or via stellar size black hole mergers. The problem for her claim that black holes are impossible is that she cannot rule out other mechanisms. I don't see any reason why primordial black holes shouldn't be possible, inflation might prevent them though. Also, the Schwartzschild radius is proportional to the mass of the star. So if two neutron stars collided the event horizon would form just as they were touching. I don't think she can easily rule out black holes forming via this mechanism. Further the metric she wrote down was spherically symmetric, so she has a non-rotating star, most stars rotate.

If she's right it would solve two problems, one is that the event horizon should take an infinite amount of time to form - as seen by an asymptotic observer. The other, as the article noted, is the quantum information problem. So I wouldn't rule it out.

Originally posted by DeepThought
I had a very quick look at the paper and it looks reasonable enough. It's enough that there is a very strong gravitational field for Hawking radiation to be emitted. In Hawking's model it is produced near an event horizon, not from it - a positive energy particle is emitted and the negative energy particle falls through the horizon. In her model it ju ...[text shortened]... The other, as the article noted, is the quantum information problem. So I wouldn't rule it out.

Did you read the full paper?

http://arxiv.org/pdf/1409.1837v1.pdf

Does she offer any explanation for the data we see that we suppose is black hole phenomena? I wonder if we have ever seen a star go in back of a black hole and disappear and then reappear after occultation?