Dummies Advocate

[AO2012]

I would like to play dummies advocate. From my understanding there are magnetic fields for just about anything with mass? And normally the more mass, the larger the field and strength of it? But, I have more mass than the magnet in my hand, which I guess is not the case in terms of density, but collectively ... it has a stronger magnetic field.

 

Anyhow, as you can see magnetism is on my brain. I would imagine there is some theoretical topic phrase for the thought experiments involving electro/magnetism and what it's like at or near BH. The questions turning my noodle stiff are, if it's ... there,

 

Is it possible for the mass that lies past the EH to ... exhibit a magnetic field/force beyond the EH?

 

Like wise, would the mass pre-EH have a field that would ... effect that of the BH?

 

Does it start to ... fold in on itself like gravity or matter does?

 

What is the name of the field concerning thoughts about this ... stuff? What's the leading theory called ... if there is something other than ... pure speculation.

[NowThatWeKnow]

... From my understanding there are magnetic fields for just about anything with mass? And normally the more mass, the larger the field and strength of it? ...

 

This is not my area of expertise but I thought the proper material was essential for a magnetic field. I thought that the strength of Earths magnetic field was influenced by it's active core more then it's size. Other expert thoughts will be interesting.

 

Edit - Are you thinking about a gravitational field rather then magnetic field?

[AO2012]

I understand this element comes into play with lesser examples, with simple magnetism. Surely there is no lack of proper material, or electrical conditions within the halves of a BH, halves being either side of an EH.

 

*edit*

I just imagine that the extreme condition (of a BH), which shows the extremes of gravity, would also be sufficient condition for extreme electromagnetic/magnetic possibility. I just imagine a BH has to have magnetic/electromagnetic properties, and I just have to imagine they are fairly extreme like is gravitational properties. I wish long ago, instead of being nudged toward art and imagination, I would have been nudged toward math and science.

Edited April 19, 2009 by AO2012

[ydoaPs]

The strength of the magnetic field is not dependent upon the mass.

 

Also, BH is black hole? What is EH?

[AO2012]

Event horizon

[Airbrush]

The original question, simply stated, is "do black holes have magnetic fields?" Good question, I don't know. Magnetars are neutron stars with fantastic magnetic fields. Black holes have mass, spin, and charge. Does any of that imply magnetic fields?

 

http://en.wikipedia.org/wiki/Magnetar

[AO2012]

Is the event horizon of a BH a perfect sphere, an infinitesimal skin, but spherical never the less, absolute?

[Airbrush]

Even an object with smaller mass, such as our Moon, is massive enough to compact itself into a sphere. A black hole event horizon must be the most perfect sphere found in nature.

[Sisyphus]

Is the event horizon of a BH a perfect sphere, an infinitesimal skin, but spherical never the less, absolute?

 

It isn't infinitessimal. The event horizon is not the singularity itself, just the boundary beyond which nothing can escape. It has finite size. It is also not necessarily spherical - rotation causes the event horizon to "bulge."

[Airbrush]

True that a BH rotating at near relativistic speeds, or I believe they stated a possible limit of 1,000 RPS? What percentage of BH are believed to be rotating at such high speed that they would bulge?

[Sisyphus]

True that a BH rotating at near relativistic speeds, or I believe they stated a possible limit of 1,000 RPS? What percentage of BH are believed to be rotating at such high speed that they would bulge?

 

Surely any rotation at all would cause some bulge. Again, though, I think we should be more specific than saying "the black hole." We're talking about the event horizon. The singularity itself is of zero volume, always, but IIRC it is ring-shaped if spinning.

[Mr Skeptic]

I'm pretty sure that an electrically charged, rotating black hole will produce a fairly impressive magnetic field.

[GDG]

Surely any rotation at all would cause some bulge. Again, though, I think we should be more specific than saying "the black hole." We're talking about the event horizon. The singularity itself is of zero volume, always, but IIRC it is ring-shaped if spinning.

 

IIRC, the event horizon does not bulge, but remains spherical. Perhaps you are thinking of the ergosphere predicted by the Kerr solution?

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True that a BH rotating at near relativistic speeds, or I believe they stated a possible limit of 1,000 RPS? What percentage of BH are believed to be rotating at such high speed that they would bulge?

 

I don't know that anyone has yet observed actual rotation of a black hole. However, when you consider that pulsars have been observed to have periods as short as 1.4 msec (700+ RPS), and conservation of angular momentum results in a higher rotation rate as the object decreases in radius, I would not be surprised to find that most black holes formed from stellar collapse had very high rotation rates.

[Airbrush]

I agree. It is far more likely that a star collapse would be a little off center, and that little bit off-center is all it takes to whip the BH into a very high speed spin.

[Sisyphus]

IIRC, the event horizon does not bulge, but remains spherical. Perhaps you are thinking of the ergosphere predicted by the Kerr solution?

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Interesting. It seems that article and the black hole article disagree (the latter saying the event horizon is an oblate spheroid). Will someone who knows more than Wikipedia chime in?

[GDG]

I agree. It is far more likely that a star collapse would be a little off center, and that little bit off-center is all it takes to whip the BH into a very high speed spin.

 

It doesn't have to collapse asymmetrically: the star is already spinning. As the radius decreases, the rotation rate has to increase. Like a spinning ballet dancer, who speeds up as she brings her arms in close.

 

For another example, find one of those playground merry-go-rounds,

Grab on, and run it around until you have it moving pretty well, then jump on, staying out at the rim. Notice the rotation rate. Now climb toward the center of the merry-go-round: you'll notice that the rotation rate speeds up quite a bit. If you get several people to copy you, you can really accelerate the rotation rate -- to a nauseating degree