Could a Black Hole destroy a whole galaxy?

[Lookingglassman]

Is it theoretically possible for a black hole at the center of our galaxy to eventually "suck down" (I dont know the right terminolgy to use) our whole galaxy? If so, wouldn't the dense core of the collpased star be larger because it would have trapped a whoel galaxy's worth of matter?

 

[All Seeing Eye]

There is already a supermassive black hole at the centre of our galaxy (thats what all the stars are orbiting around) and I think its already sucked in everything it can, even supermassive black holes can only suck matter in at a certain distance. If our sun turned into a black hole it would only be able to suck in matter as far out as its gravity reached when it was a sun and that works the same with supermassive black holes, it would have to be insanely big on a galaxy wide scale to suck a galaxy in.

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

 

[Neopeius]

Starblazers said:
Is it theoretically possible for a black hole at the center of our galaxy to eventually "suck down" (I dont know the right terminolgy to use) our whole galaxy? If so, wouldn't the dense core of the collpased star be larger because it would have trapped a whoel galaxy's worth of matter?

Well, you have to remember that black holes don't create extra suction. They are simply the end of the lifecycle of a big star, or in the case of the center of a galaxy, lots and lots of stars.

The stars in the rest of the galaxy still orbit around the center, and it's unlikely that many of them will be perturbed from their orbit enough to become part of the supermassive center. Sort of like if you turned the sun into a black hole (without any intermediary steps), it would be a very tiny thing now, but it would have the same mass. Things would get very cold in the solar system, but the orbits of the planets would remain unchanged.

We certainly haven't seen any indication that black holes "devour" galaxies. I think the biggest one we've found has a mass of "only" a few billion suns.

 

[Meredith]

You would have to make a huge ass funnel and funnel the stars and planets and dust directly to the Black hole.

If you want to destroy a galaxy an easier way to to create a false vaccum collapse, but be careful not to destroy the entire universe.

 

[Ariadne]

Neopeius said:

Starblazers said:
Is it theoretically possible for a black hole at the center of our galaxy to eventually "suck down" (I dont know the right terminolgy to use) our whole galaxy? If so, wouldn't the dense core of the collpased star be larger because it would have trapped a whoel galaxy's worth of matter?

Well, you have to remember that black holes don't create extra suction. They are simply the end of the lifecycle of a big star, or in the case of the center of a galaxy, lots and lots of stars.

The stars in the rest of the galaxy still orbit around the center, and it's unlikely that many of them will be perturbed from their orbit enough to become part of the supermassive center. Sort of like if you turned the sun into a black hole (without any intermediary steps), it would be a very tiny thing now, but it would have the same mass. Things would get very cold in the solar system, but the orbits of the planets would remain unchanged.

We certainly haven't seen any indication that black holes "devour" galaxies. I think the biggest one we've found has a mass of "only" a few billion suns.

Would the stars not eventually (i.e. trillions or more years from now) lose enough energy to fall into the centre, due to gravity?

Like the planets will eventually lose energy and fall into the sun...

 

[Lookingglassman]

Thanks for all the answers. I was just wondering because I thought black holes pulled in matter sort of like a giant whirpool in the water and that eventually a whole galaxy would be pulled into it.

 

[Manticore]

Toresica said:

Neopeius said:

Starblazers said:
Is it theoretically possible for a black hole at the center of our galaxy to eventually "suck down" (I dont know the right terminolgy to use) our whole galaxy? If so, wouldn't the dense core of the collpased star be larger because it would have trapped a whoel galaxy's worth of matter?

Well, you have to remember that black holes don't create extra suction. They are simply the end of the lifecycle of a big star, or in the case of the center of a galaxy, lots and lots of stars.

The stars in the rest of the galaxy still orbit around the center, and it's unlikely that many of them will be perturbed from their orbit enough to become part of the supermassive center. Sort of like if you turned the sun into a black hole (without any intermediary steps), it would be a very tiny thing now, but it would have the same mass. Things would get very cold in the solar system, but the orbits of the planets would remain unchanged.

We certainly haven't seen any indication that black holes "devour" galaxies. I think the biggest one we've found has a mass of "only" a few billion suns.

Would the stars not eventually (i.e. trillions or more years from now) lose enough energy to fall into the centre, due to gravity?

Like the planets will eventually lose energy and fall into the sun...

No, and no. The planets aren't going to fall into the sun, the sun is going to expand out to them (and only the inner planets too). An object in orbit is fairly stable, at least ones that have been in orbit for billions of years.

 

[Neopeius]

Toresica said:


Like the planets will eventually lose energy and fall into the sun...

There's no friction in space, or at least, a vanishingly small amount. Bodies in motion will stay in motion.

 

[Ronald Held]

I theorize that dynamical friction considerations could add to the black hole mass, but not have it absorb all of the stars in its galaxy.

 

[Neopeius]

Ronald Held said:
I theorize that dynamical friction considerations could add to the black hole mass, but not have it absorb all of the stars in its galaxy.

Theorize or Hypothesize?

 

[Ariadne]

Neopeius said:

Toresica said:
Like the planets will eventually lose energy and fall into the sun...

There's no friction in space, or at least, a vanishingly small amount. Bodies in motion will stay in motion.

Aye, but the planets are (slightly) charged and thus radiate energy.

(At least, according to my 2nd year E&M prof...)

 

[FemurBone]

As long as everything in the galaxy maintains orbital velocity around the super massive black hole, nothing will get sucked in.

Now if everything in the galaxy suddenly stopped moving around the supermassive black hole, then everything in the galaxy would begin moving towards it.

 

[The Borg Queen]

If our sun was a black hole, it would make no difference to us here on Earth as it would still have the same amount of gravitational pull, the sun would just be the size of a tennis ball or something.

 

[Meredith]

FemurBone said:
As long as everything in the galaxy maintains orbital velocity around the super massive black hole, nothing will get sucked in.

Now if everything in the galaxy suddenly stopped moving around the supermassive black hole, then everything in the galaxy would begin moving towards it.

still it would take millions of years and most objects would just slingshot or gain highly eliptical orbits around the blackhole.

 

[Neopeius]

I bet you could play cosmic billiards, aiming two galaxies *just so* to rob each other of their momentum and merge in a way which made the internal black holes much larger.

 

[Johnny Rico]

Would a super massive black hole suck in a galaxy? No. Why? Simple...the distances between celestial bodies is just too great. And the fact, like others have said, because everything in orbit around these blackholes, they remain in orbit.

Secondly, not all black holes, massive or not, are always active. Active, as in actually sucking things in. They go dormant just like volcanoes go dormant.


And thirdly, but in a slightly different side of the topic, GALAXY COLLISIONS. Would celestial bodies in galaxies collide if and when two galaxies collide? No...once again, the distances between bodies are just too great. Oh, a few might out of bad luck, but most would pass through without contact.

 

[FemurBone]

The Borg Queen said:
If our sun was a black hole, it would make no difference to us here on Earth as it would still have the same amount of gravitational pull, the sun would just be the size of a tennis ball or something.

That would depend on how far the event horizon reached. The sun may be the size of a tennis ball, but if the event horizon extends to where we are, then we would be instantly sucked in. If Earth remained outside the event horizon, then the orbital velocity of the Earth may have to increase in order to stay in orbit. Otherwise we would eventually get sucked in.

But fortunately, the sun isn't anywhere near massive enough to become a black hole. The sun will end its life as a white dwarf.

 

[Neopeius]

FemurBone said:

The Borg Queen said:
If our sun was a black hole, it would make no difference to us here on Earth as it would still have the same amount of gravitational pull, the sun would just be the size of a tennis ball or something.

That would depend on how far the event horizon reached. The sun may be the size of a tennis ball, but if the event horizon extends to where we are, then we would be instantly sucked in. If Earth remained outside the event horizon, then the orbital velocity of the Earth may have to increase in order to stay in orbit. Otherwise we would eventually get sucked in.

But fortunately, the sun isn't anywhere near massive enough to become a black hole. The sun will end its life as a white dwarf.

True that.

The event horizon of a sun is 3km. The event horizon the only applicable way to measure the *size* of black hole, as opposed to its mass. Because a black hole is always in the act of contracting, it does not have a measurable radius.

I think.

 

[Ariadne]

Johnny Rico said:
Secondly, not all black holes, massive or not, are always active. Active, as in actually sucking things in. They go dormant just like volcanoes go dormant.

How does that work?

 

[Neopeius]

Toresica said:

Johnny Rico said:
Secondly, not all black holes, massive or not, are always active. Active, as in actually sucking things in. They go dormant just like volcanoes go dormant.

How does that work?

It's not like a geological phenomenon. All "active" and "dormant" refers to is whether a particular black hole is sucking in matter at the moment.

Since the entry of lots of matter into an event horizon is accompanied by a nice burst of energy, the black holes seem to flare into life. However, the black hole itself remains unchanged, save for an increase in mass.


It's not as if black holes turn off for a while, and then suddenly get hungry and reach out at the nearest star.