It seems from research I’ve read that the supermassive blackhole at the centre of most galaxies has a direct influence on the galaxies evolution. What would happen if that blackhole ceased to exist, would it be catastrophic for the galaxies future.
Cymek said:
It seems from research I’ve read that the supermassive blackhole at the centre of most galaxies has a direct influence on the galaxies evolution. What would happen if that blackhole ceased to exist, would it be catastrophic for the galaxies future.
how would a black hole cease to exist?
Cymek said:
It seems from research I’ve read that the supermassive blackhole at the centre of most galaxies has a direct influence on the galaxies evolution.
in what way do the BHs at the centre of galaxies influence the evolution of a galaxy?
The_observer said:
Cymek said:
It seems from research I’ve read that the supermassive blackhole at the centre of most galaxies has a direct influence on the galaxies evolution. What would happen if that blackhole ceased to exist, would it be catastrophic for the galaxies future.
how would a black hole cease to exist?
I don’t know just wondering what would happen if it did.
Leaving aside how it would cease to exist (let us assume it was by magic):
The mass of this black hole is very small compared to the mass of the galaxy: perhaps something like one part in a hundred thousand.
The galaxy should stay together even if that black hole goes away.
diddly-squat said:
Cymek said:
It seems from research I’ve read that the supermassive blackhole at the centre of most galaxies has a direct influence on the galaxies evolution.
in what way do the BHs at the centre of galaxies influence the evolution of a galaxy?
http://www.cosmotography.com/images/supermassive_blackholes_drive_galaxy_evolution_2.html
Like discovering a neighborhood house assumed to be vacant is actually inhabited, over the past decade researchers realized that most galaxies have at least one black hole in residence in their central regions. But these black holes aren’t the stellar variety with three to ten times the mass of our Sun. Their size swamps the imagination- they have millions, sometimes billions, of solar masses. Even our home galaxy, the Milky Way, has a four million solar mass black hole located at its center, about 27,000 light years from Earth. Galactically speaking, that places it in our own backyard! Well, there goes the neighborhood!
At the heart of virtually every large galaxy lurks a supermassive black hole with a mass of a million to more than a billion times our Sun. Most of these black holes are dormant, but a few per cent are ‘active’ meaning that they are drawing material from their host galaxy inwards, This forms an accretion disc that feeds the black hole.
As the material spirals through the disc toward the event horizon, it gains fantastic speed and releases vast amounts of energy. As a result, some of the disk material does not fall in because its speed achieves escape velocity. This material is slung around to one of the poles and expelled as a powerful jet traveling near the speed of light.
Image credit: Wolfgang Steffen, Cosmovision
We also now know that supermassive black holes are inexorably linked to the galaxies that encircle them.
For example, the size of a supermassive black hole appears to have a direct correlation to the galaxy where it exists. Almost a decade ago, researchers calculated that the mass of a supermassive black hole appeared to have a constant relation to the mass of the central part of its galaxy, known as its bulge (think of the yolk in a fried egg). This 1 to 700 relationship supports the notion that the evolution and structure of a galaxy is closely tied to the scale of its black hole.
Other studies found another strong correlation. This one was between the mass of a supermassive black hole and the orbital speed of stars in the outer regions of their galaxy where the direct gravitational influence of the supermassive black hole should be weak: the larger the black hole, the faster the outer stars travel.
Thus it’s now believed that black holes are not only common throughout the Cosmos but they play a fundamental role in the formation and evolution of the Universe we inhabit today.
“This 1 to 700 relationship supports the notion that the evolution and structure of a galaxy is closely tied to the scale of its black hole. “
True but the causality is probably that a more massive galaxy is going to form a more massive black hole…
As I understand it, it is still an open question as to whether supermassive BHs initially form first and then seed the formation of the galaxy around them, or whether the galaxy forms and produces a BH at the centre. Certainly it seems that BH mergers during galaxy collisions is an important process.
dv said:
Leaving aside how it would cease to exist (let us assume it was by magic):The mass of this black hole is very small compared to the mass of the galaxy: perhaps something like one part in a hundred thousand.
The galaxy should stay together even if that black hole goes away.
“This 1 to 700 relationship supports the notion that the evolution and structure of a galaxy is closely tied to the scale of its black hole. “
True but the causality is probably that a more massive galaxy is going to form a more massive black hole…
I totally agree with DV here. It’s not that the evolution of the galaxy depends on the black hole, but rather that the size of the black hole depends on the evolution of the galaxy.
“The galaxy should stay together even if that black hole goes away.”
But would it stay together in exactly the same way, or would there be detectable shifts due to other forces that had been quashed by the effects of the BH?
mollwollfumble said:
I totally agree with DV here. It’s not that the evolution of the galaxy depends on the black hole, but rather that the size of the black hole depends on the evolution of the galaxy.
As I pointed out, this is not a fact.
Divine Angel said:
“The galaxy should stay together even if that black hole goes away.”But would it stay together in exactly the same way, or would there be detectable shifts due to other forces that had been quashed by the effects of the BH?
The BH, per se, has no ‘other forces’ than gravity. (Actually they can have electric charge as well but that is unlikely to be significant in a stellar BH let alone a supermassive BH.)
The accretion disk around a BH can have some funky effects so this aspect of the question will depend on whether you are talking about an Active Galaxy or not.
I was thinking “tidal forces” but I wasn’t sure what I meant by that.
Tidal forces are gravitational.
Specifically gravitational effects on an extended body (ie large in size) in a non-uniform gravitational field.
Without the presence of a BH, could there be other external gravitational influences on a galaxy?
I don’t understand the question.
1) there always are external gravitational influences on a galaxy, namely from other nearby galaxies.
2) the effect of a supermassive BH is not ‘external’ it is internal to a galaxy.
With the influence of a BH, it would override any external forces. Without a BH, what other forces are acting upon a galaxy?
MartinB said:
Tidal forces are gravitational.
Now slow down Egghead
Divine Angel said:
With the influence of a BH, it would override any external forces.
No. As pointed out above, the BH is only a small part of the mass, and hence self-gravitation, of the galaxy.
Divine Angel said:
Without a BH, what other forces are acting upon a galaxy?
With or without a BH, gravity from other nearby galaxies is acting on a galaxy. The difference in the effect of this force is not significantly different with or without a BH.