Why Some Supermassive Black Holes Have Big Jets

astroengine writes "Some of the supermassive black holes at the centers of galaxies have powerful jets blasting from their poles, and others have weak jets, but many don't have jets at all. Why is this the case? In new simulations carried out by astronomers at NASA and MIT, it would appear that the way in which the black hole spins relative to its accretion disk may be a contributing factor. Strangely enough, the results indicate that if the black hole rotates in the opposite direction to its accretion disk, the most powerful jets form. The region between the black hole event horizon and the accretion disk still baffles scientists, so these simulations are very speculative, but the results seem to match what radio astronomers are seeing in the cores of active galaxies. Perhaps it's time to fire up that event horizon telescope!"

Re:Here's a silly question

[drinkypoo]

Is there a name for the theory that matter is being sucked out of our universe as fuel for another?

Kind of hard to reconcile since black holes increase in mass as they draw in matter (aka mass.)

Re:Here's a silly question

[newcastlejon]

They increase in mass, yes but does their size increase? Where does the matter go if it's all compressed to a singularity? Are all the atoms just spaghettified, stacked one on top of the other in some infinitely tall, infinitely narrow well?

I have only a most basic grasp of cosmology but it's an interest of mine and I recall watching something on documentary heaven to the effect that black holes may well be a universe of their own. To be honest the very idea of a singularity still baffles me: it seems as though you start with an assemblage of simple, dull matter and in the blink of an eye any semblence to matter as we know it disappears and you're left with something that - to me at least - sounds like a feature of space itself.

Exactly what happens between the instant when you have a very, very dense lump of matter and an infinitely dense one? It seems an infantile question but where did all the matter go? Or was it transformed into something else that has mass but no size? Thinking about it gives me a headache and usually leaves me pondering whether any particles really have a physical size or if it's just another consequence of our limited view of the Universe.

Re:I'm not qualified to read this article.

[maxwell demon]

For a rotating black hole, the singularity is not a point, but a ring. [wikipedia.org]

Re:Here's a silly question

[Barrinmw]

Actually, math only breaks down at the Event Horizon, and physicists pretty much ignore that one point and continue on. Theoretically, due to all calculations, time at the singularity proceeds just like it does for a non-relativistic observer. And you can in fact, calculate the amount of time it would take for you to reach the center of the black hole, though somebody watching you would say it took an infinite amount of time since they see you as stopping at the Event Horizon. But to you, you actually reach the Singularity.

Re:I'm not qualified to read this article.

[Sir_Lewk]

If the spin of a black hole can be determined across a black hole, does that mean information can be transmitted across the event horizon?

Re:Wrong answered with wrong modded informative

[syousef]

black holes do not absorb dark matter
http://www.universetoday.com/2010/03/22/astronomers-find-black-holes-do-not-absorb-dark-matter/#more-60422 [universetoday.com]

So this would suggest the darkmatter particle has no mass, travels faster than light or both?

I skimmed their journal article on arxiv. At this stage all they've shown is that there is an upper limit to the amount of matter in the central region of a galaxy given that we don't see a "runaway accretion" (presumably the whole galaxy goggled up by the black hole?). They conclude this suggests that the centers of galaxies have constant density.

So they seem to be saying dark matter doesn't live there (or that there is a limit to it) and that is how it avoids being sucked into the black hole.

Re:Good reading here

[RulerOf]

What happens when one black hole eats another?

Nothing special. The theory is that the "snap" happens at the moment a singularity is formed. It doesn't depend on it at all after that point.

Re:Wrong answered with wrong modded informative

[drinkypoo]

3) What's even more interesting is that recent work suggests black holes do not absorb dark matter

What's even more interesting is that your link doesn't suggest that black holes do not absorb dark matter:

The researchers modeled the way in which the dark matter is absorbed by black holes and found that the rate at which this happens is very sensitive to the amount of dark matter found in the black holes' vicinity. If this concentration were larger than a critical density of 7 Suns of matter spread over each cubic light year of space, the black hole mass would increase so rapidly, hence engulfing such large amounts of dark matter, that soon the entire galaxy would be altered beyond recognition.

It doesn't say they don't absorb it, only that our assumptions of how they would absorb it are wrong. It also says dark matter resists 'assimilation' into a black hole, not that it is immune to it. If they actually meant to say that it cannot be absorbed by a black hole, they need to study English, because they utterly failed everywhere but the subject, which does not agree with the article.