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Gamefreak89
2010-Nov-04, 11:48 AM
In terms of light years what is the closest stellar mass Black Hole? How long does it take for a Black Hole to Move from one star system to the next? As in 10 to 50 light years apart in distance.

Strange
2010-Nov-04, 12:07 PM
Sounds like the closest likely black hole is Cygnus X-1 at 6,000 light years (http://en.wikipedia.org/wiki/Cygnus_X-1). There is also the black hole at the center of the galxy (http://en.wikipedia.org/wiki/Sagittarius_A*) and V4641 (http://en.wikipedia.org/wiki/V4641_Sagittarii).


How long does it take for a Black Hole to Move from one star system to the next?

Not sure why you would expect a black hole to move between star systems. I assume that is no more likely than stars doing the same thing.

Spoons
2010-Nov-04, 12:13 PM
I would expect the black holes to be much more of an anchor point than a star system, but all this movement of space objects is pretty much relative anyway, isn't it?

Gamefreak89
2010-Nov-04, 12:33 PM
Well on the term of a "Rouge Black Hole" If they exist being is it possible for them to move in different directions relative to the movement of the galaxy?

AndreasJ
2010-Nov-04, 12:49 PM
Well on the term of a "Rouge Black Hole"
Black holes prefer mascara. :p


If they exist being is it possible to for them to move in different directions relative to the movement of the galaxy?

Stellar-mass black holes (the sort we're likely to find in the astronomical neighbourhod) move basically like stars, mostly in approximately circular orbits around the galactic centre. Some of them (like Cygnus X-1) are gravitationally bound to still-stellar companions, the rest orbitly alone, only very occasionally having close chance encounters with other stellar systems. Note that due to proper motion, the stars nearby the Sun - or any other star in a similar orbit - change over millions and tens of millions of years; few if any of our current neighbours were anywhere close to the Sun an orbit (~225 million years) ago.

Does that answer your question?

Cougar
2010-Nov-04, 12:55 PM
Well on the term of a "Rouge Black Hole" ....

Make up your mind - is it rouge (red) or is it black? :razz: Oh, you mean rogue black hole. Think of how stellar mass black holes form - from the collapse of a very large star at the end of its life. An asymmetric collapse will likely just result in a lot of spin as opposed to kicking the object off in one direction or another. I guess it's possible, but it seems very difficult and unlikely to come up with a rogue black hole coursing through a galaxy....

George
2010-Nov-04, 03:09 PM
Make up your mind - is it rouge (red) or is it black? :razz: Redish-black would suggest a hot accretion disk. :)

JCoyote
2010-Nov-04, 03:12 PM
Our galaxy is busy colliding with another galaxy. I don't think any other excuse is needed for star systems encountering each other when you are mixing orbital patterns of 2 different systems. Yes, it's unlikely, but on the other hand, there is a force called gravity that increases the odds.

The biggest problem with a stellar mass black hole in interstellar space without a significant current food source is... you might not be able to detect it until it was really close. I would expect gravitational lensing to be the first indicator and even that might be "huh, some dust must have floated past the lens here" until it was pretty profound.

Grey
2010-Nov-04, 03:57 PM
Just as an exercise, we could assume the worst. :) Imagine there's a rogue stellar mass black hole about ten light years away, as close as some of the nearest stars. That's far closer than any known black hole. For that matter, it's closer than anything we've observed that could even possibly be a black hole (heck, there are only 12 stellar objects that close), but one could perhaps claim that we can't see it because it has already absorbed most of the gas and dust in its immediate neighborhood. Say it's counter-rotating around the galaxy with a velocity comparable to that of the Sun's orbital velocity around the galaxy, and headed straight for us. So our relative velocity with it would be a speedy 440 km/sec; that's about the fastest that anything could reasonably be expected to be moving toward us. At that rate, it would get here in something like 6,500 years. Pretty short in geologic or stellar time; pretty long in human terms.

JCoyote, what galaxy collision are you thinking of? It's true that the Milky Way is pretty much constantly in the process of absorbing some of the nearby dwarf galaxies, but to my knowledge, none of that is happening anyplace particularly close to the solar neighborhood, and we're certainly not currently involved in a merger with any major galaxies.

PhillipJFry
2010-Nov-04, 04:08 PM
Sounds like the closest likely black hole is Cygnus X-1 at 6,000 light years (http://en.wikipedia.org/wiki/Cygnus_X-1). There is also the black hole at the center of the galxy (http://en.wikipedia.org/wiki/Sagittarius_A*) and V4641 (http://en.wikipedia.org/wiki/V4641_Sagittarii).



Not sure why you would expect a black hole to move between star systems. I assume that is no more likely than stars doing the same thing.

According to this link http://www.nrao.edu/pr/2000/v4641/ the nearest (discovered) BH is 1600 ly away.

Strange
2010-Nov-04, 04:11 PM
According to this link http://www.nrao.edu/pr/2000/v4641/ the nearest (discovered) BH is 1600 ly away.

The Wikipedia entry [insert appropriate caveat here] says that this original distance estimate was incorrect: "later observations showed it to be at least 15 times further away" (with reference to http://arxiv.org/abs/astro-ph/0103045v1).

PhillipJFry
2010-Nov-04, 04:15 PM
The Wikipedia entry [insert appropriate caveat here] says that this original distance estimate was incorrect: "later observations showed it to be at least 15 times further away" (with reference to http://arxiv.org/abs/astro-ph/0103045v1).

Ah, my bad. :-)

antoniseb
2010-Nov-04, 05:10 PM
... the nearest (discovered) BH is 1600 ly away.

There are probably numerous stellar mass black holes closer than this (hence PJF's use of the word Discovered). We only see the bright ones that are accreting stuff. You can assume that there is some number of stellar mass black holes in the Milky Way orbiting out by us, including (as has been noted) things in the Arcturus stream, or from other mergers. How many? Probably millions, probably not billions. The actual number can be guessed through our IMF approximations. Let's say that in the zone 20 to 30 thousand light years from the center of the galaxy, in a swath 3000 light years thick (about 5 trillion cubic light years), there are 10,000,000 stellar mass black holes (a plausible, but not narrowly defined guesstimate). That would mean there's about 500,000 cubic light years per stellar mass black hole, i.e. each would be in a box about 90 light years on a side.

Concerning speed, you can expect that new ones might be traveling relative to our stream at a few miles per second, and that old ones might be traveling up to 50 to 100 miles per second.

Gamefreak89
2010-Nov-04, 10:35 PM
So say like we discovered a BH that is in a approximate distance of 5 to 7 light years from us, in a human time span and given its angle of trajectory and velocity how long would it take to get closer to us or even affect our Star system's gravitational orbit?

Strange
2010-Nov-04, 10:46 PM
So say like we discovered a BH that is in a approximate distance of 5 to 7 light years from us, in a human time span and given its angle of trajectory and velocity how long would it take to get closer to us or even affect our Star system's gravitational orbit?

Google, as always, is your friend: (7 light years) / (100 (miles per second)) = 13,039.7678 years

astromark
2010-Nov-05, 01:00 AM
Lets just take a few deep breaths and relax a little. We do not know of a stellar mass object coming this way. Black holes included.

Black holes are not that hard to find. Invisible only if you ignore the swath of debris orbiting it...

and the effect its menacing gravity has on near to it objects... invisible, no.

However... There could be a nasty little surprise waiting yet to be created just under the French Swiss boarder...

How will we know... Phoffff T. ! ...gone. We will never know.:wall::Lol:

Gamefreak89
2010-Nov-05, 02:06 AM
Lets just take a few deep breaths and relax a little. We do not know of a stellar mass object coming this way. Black holes included.

Black holes are not that hard to find. Invisible only if you ignore the swath of debris orbiting it...

and the effect its menacing gravity has on near to it objects... invisible, no.

However... There could be a nasty little surprise waiting yet to be created just under the French Swiss boarder...

How will we know... Phoffff T. ! ...gone. We will never know.:wall::Lol:

LOL! yeah the LHC joke that one always cracks me up :D. But correct me if I'm wrong but if a black hole was entering a solar system then wouldn't it take decades just to reach the host star itself? Ok in other words black hole travels... darn it I don't know how the distance right when you are not using light years, what about AU's don't they work into the equation as well? If you are not calculating light years?

astromark
2010-Nov-05, 03:22 AM
A side issue for Gamefreake; Yes we could use AU's ( astronomicle units. ) It being one Earth-Sun distance.

It is many AU's to the edge of the solar system. Distances beyond that are so great that we prefer the light year.

ly. As it covers the distances simpler.. smaller numbers seem to be easy to imagine... :worried:( that's not true )

I put it like this... Light travels very quickly through the vacuum of space. Proximately 300,000 km / sec. That's 186,000 miles / sec.

About seven times around the earth in a second or to the moon in just 1.2 sec. Making the AU just 8.25 mins., away... Earth Sun distance.

So if you do not like the ly.. Then just multiply it by 8.25 to make into AU's.

Pulling this back to this subject of the distances to near to us black holes... many.

As you seem to have grasped this already...

The distances are great. the velocity is not so fast... the time period would be measured in thousands of years,

and we know of no such object at this time coming this way at all.

Just as a aside point... yes. If a stellar mass object were any place near this solar system... we would know already.

The motions of the outer planets would have given up its path years ago...

Gamefreak89
2010-Nov-05, 03:27 AM
That is a long distance but from what I've learned about Black Holes is that when they eat more matter they gain more mass right? Correct me if I'm wrong so the bigger the Black Hole the slower it moves or is it the other way around?

WayneFrancis
2010-Nov-05, 03:29 AM
I would expect the black holes to be much more of an anchor point than a star system, but all this movement of space objects is pretty much relative anyway, isn't it?

black hole will orbit the centre of the galaxy just like any equivalent mass star would.

WayneFrancis
2010-Nov-05, 03:30 AM
Well on the term of a "Rouge Black Hole" If they exist being is it possible for them to move in different directions relative to the movement of the galaxy?

Yes....if the black hole was part of something like a galaxy merger then it could quite possibly have a retrograde orbit.

WayneFrancis
2010-Nov-05, 03:55 AM
So say like we discovered a BH that is in a approximate distance of 5 to 7 light years from us, in a human time span and given its angle of trajectory and velocity how long would it take to get closer to us or even affect our Star system's gravitational orbit?

That is a bit like asking "How long would it take to get close to NY if you started 200 miles away"
There is no issue with black holes more then normal stellar objects as far as danger goes. In fact stars can be much more dangerous then black holes because of radiation.

If a 3 solar mass black hole entered our solar system we'd be just as ... err ... in trouble as if a star entered in our solar system.

Nick Theodorakis
2010-Nov-05, 04:08 AM
Anybody thinking of Fritz Leiber's story, "A Pail of Air"?

Nick

WayneFrancis
2010-Nov-05, 04:12 AM
That is a long distance but from what I've learned about Black Holes is that when they eat more matter they gain more mass right? Correct me if I'm wrong so the bigger the Black Hole the slower it moves or is it the other way around?

Any black hole travelling through the galaxy and "eating" other matter will just take on that potential energy as far as an external observer is concerned. That means it may gain or loose speed relative to you. Gaining mass, in itself, doesn't make the black hole slow down.

Take this as an example
http://www.users.on.net/~waynefrancis/merger.png

The vectors just get added together.

The rate of spin for a black hole can change as it feeds but this is just the conservation of angular momentum.

Gamefreak89
2010-Nov-05, 04:22 AM
Interesting hmm I wonder what's worst getting our planet thrown out of our solar system and being frozen to death or being sucked up by a black hole? I wonder what is more pleasant lol? (Being Sarcastic of course) I believe that the only way for a star to just wander into our solar system if its part of a binary pair correct? and I also believe that if both of these stars are orbiting around a Black Hole then one gets sucked up while the other is thrown out (Very rarely it happens I believe) . Also when you say angular of momentum that is the law at which objects spins on its axis right?

antoniseb
2010-Nov-05, 10:48 AM
Lets just take a few deep breaths and relax a little. We do not know of a stellar mass object coming this way. ...
I've been assuming that gf89's been gathering ideas for a story line, not looking at a real threat.

chornedsnorkack
2010-Nov-05, 12:10 PM
There are probably numerous stellar mass black holes closer than this (hence PJF's use of the word Discovered). We only see the bright ones that are accreting stuff. You can assume that there is some number of stellar mass black holes in the Milky Way orbiting out by us, including (as has been noted) things in the Arcturus stream, or from other mergers. How many? Probably millions, probably not billions. The actual number can be guessed through our IMF approximations. Let's say that in the zone 20 to 30 thousand light years from the center of the galaxy, in a swath 3000 light years thick (about 5 trillion cubic light years), there are 10,000,000 stellar mass black holes (a plausible, but not narrowly defined guesstimate). That would mean there's about 500,000 cubic light years per stellar mass black hole, i.e. each would be in a box about 90 light years on a side.


Can we rule out billions?

A big part bright visible stars we see are OB dwarfs, which are very few in number but bright. Yet they are short lived - under 100 million years. Most of the rest we see are red giants that also are short lived and few in number. Most stars in any defined volume of space, such as Solar neighbourhood are K and M dwarfs, which last longer than the age of world.

But neutron stars and especially black holes last forever. The stars that eventually burn out to black holes do so in under 10 million years, but the world has lasted over 10 milliards of years and all the black holes made over the thousands of generations of stars are still around. Black holes should outnumber O dwarfs thousands of times, even more so if young Milky Way held more O dwarfs than now.

On the other hand, the ratio of M dwarfs to K dwarfs should be unchanged, because even the brightest K0 dwarfs have not yet burnt out.

What is the number ratio of K dwarfs to white dwarf remnants of intermediate mass stars? What is the number ratio of white dwarfs to neutron stars? Neutron stars to black holes?

Red dwarfs have minimum brightness and shine consistently over milliards of years, such that they can be seen in visible. White dwarfs have smaller radiating area, but they cool slowly and the eldest are still at 4000 K, so they can be seen in visible as well. But how can old neutron stars and old black holes be seen?

How much gas would a Population II neutron star be accreting from the Local Bubble interstellar gas passing through at 100 km/s? How about a Population II black hole?

All gravitational energy of accreting gas must be radiated by a neutron star, somewhere in far UV or mild roentgen rays. Are any neutron stars seen in thermal surface radiation that are not pulsars?

A black hole has event horizon instead of surface. So infalling gas may simply carry its energy beyond event horizon instead of radiating it. Or when it misses the event horizon, it can simply pass on the hyperbolic orbit and also radiate nothing. What is theoretical minimum brightness of a black hole that is accreting interstellar gas?

antoniseb
2010-Nov-05, 12:54 PM
Can we rule out billions? ...
Rule out absolutely? Maybe not, but what I was giving a number for was the doughnut shaped space between 20 and 30 thousand light years from the center of the galaxy. The question is: how many stars big enough to form stellar mass black holes have been created in that zone? I have the impression that well less than 1% of all new stars are large enough. There's about 100 billion stars in the galaxy (depending on where you draw the line at the low end) - maybe 30 billion on that zone. So I said "not biilions". BTW, I'm guessing thlere are probably about ten times as many (give or take a factor of ten - i.e old school astronomy) neutron stars as stellar mass black holes. In my opinion for gf's original query, you are right to include them. They'd have roughly the same effect.

Jeff Root
2010-Nov-05, 01:20 PM
Wayne left the word "doesn't" out of his last post.

-- Jeff, in Minneapolis

neilzero
2010-Nov-05, 01:52 PM
I agree with chrorned: Black holes could out number visible stars in our galaxy. If so, one is likely about 4 light years from Earth at present. The probability is 50% it is approaching Earth at present, and the closest approach will be about two light years. Even at 10 solar mass, our outer planets will be perturbed only slightly from a distance of 2 light years. Our Oort cloud could send us comets twice as often starting a few thousand years after the closest approach of 2 light years. The approach vector could be 0.01% of c (the probability is very low for a faster approach vector) It will be at about 3 light years in 10,000 years. The next light year, will take longer due to the vector, so we can be reasonably sure a close approaching black hole is not a near term probability. Other than the black holes at centers of galaxies, more than ten solar mass black holes are likely rare. Detectability of a ten solar mass black hole at 4 light years is about 50% ? since lone black holes typically have very weak accretion disc, as interstellar space has negligible matter to collect. Neil

Grey
2010-Nov-05, 02:44 PM
But correct me if I'm wrong but if a black hole was entering a solar system then wouldn't it take decades just to reach the host star itself?It depends on just where you define the edge of the solar system, and exactly how fast it's moving (and which direction it's going). For example, an object at Pluto's orbit heading straight for the Sun at, say, 200 km/sec would get there in about a year. On the other hand, something further out that's starting at negligible velocity but accelerating due to gravity (essentially coming in at solar escape velocity, the slowest something could reasonably be coming), it would indeed take decades. Of course, if there were any kind of stellar mass object anywhere near that close, we'd already be noticing its gravitational effects. I wouldn't lie awake at night worrying about whether a black hole is going to come destroy the solar system. :)

AndreasJ
2010-Nov-05, 03:38 PM
I agree with chrorned: Black holes could out number visible stars in our galaxy.
Not likely. It would require massive stars to be born at a higher rate than smaller ones, which isn't what we observe in star-forming regions.

chornedsnorkack
2010-Nov-05, 04:17 PM
BTW, I'm guessing thlere are probably about ten times as many (give or take a factor of ten - i.e old school astronomy) neutron stars as stellar mass black holes.
How do you derive this number? Consider that all known neutron stars are within a narrow mass range of 1,44 to 1,97 solar masses....

antoniseb
2010-Nov-05, 04:53 PM
How do you derive this number? Consider that all known neutron stars are within a narrow mass range of 1,44 to 1,97 solar masses....

I gave my derivation in that post i.e. I guessed based on my recollection of the initial mass function. Please note that neutron stars do NOT start off as main sequence stars with mass from 1 to 2 solar masses. They start off much heavier, and have a large range of initial sizes that will eventually boil down to a post SN core of neutron star mass.

chornedsnorkack
2010-Nov-05, 06:02 PM
Out of the 109 stars within 20 lightyears of the Sun - the list is reasonably complete because even brown dwarfs are detected - 6 are white dwarfs. So white dwarfs number in milliards.

It is a reasonable guess that the black holes and neutron stars combined are fewer than a milliard, maybe. But are neutron stars the prevalent fate of stars too massive to become white dwarfs? Or will neutron stars only form from a small fraction of massive stars near the mass threshold, and be outnumbered by black holes?

Asking again - are any neutron stars, at all, observed by their thermal radiation alone in the absence of any and all pulsar activity? How visible is a non-pulsar neutron star, and what are the observational lower bounds on the distance they may be from us?

Nereid
2010-Nov-05, 06:20 PM
Out of the 109 stars within 20 lightyears of the Sun - the list is reasonably complete because even brown dwarfs are detected - 6 are white dwarfs. So white dwarfs number in milliards.

It is a reasonable guess that the black holes and neutron stars combined are fewer than a milliard, maybe. But are neutron stars the prevalent fate of stars too massive to become white dwarfs? Or will neutron stars only form from a small fraction of massive stars near the mass threshold, and be outnumbered by black holes?

Asking again - are any neutron stars, at all, observed by their thermal radiation alone in the absence of any and all pulsar activity? How visible is a non-pulsar neutron star, and what are the observational lower bounds on the distance they may be from us?
Have you heard of GemingaWP (http://en.wikipedia.org/wiki/Geminga)?

One difficulty with these kinds of calculations is the fact that stars are often found in binary systems, some of which are close.

chornedsnorkack
2010-Nov-05, 09:16 PM
Have you heard of GemingaWP (http://en.wikipedia.org/wiki/Geminga)?
.
I had - but I thought it was a (gamma-ray) pulsar.

However, now I found about Magnificent Seven - which, though weakly periodic, do seem to be thermal emitters.

But they, like Geminga, are mere few million years old. How bright would 10+ milliard year old neutron stars be?

Gamefreak89
2010-Nov-06, 04:44 AM
I understand what everyone is saying (Besides the math part of course which I'm not so good at) Angular Momentum: In physics, angular momentum, moment of momentum, or rotational momentum[1][2] is a conserved vector quantity that can be used to describe the overall state of a physical system. The angular momentum L of a particle with respect to some point of origin is

where r is the particle's position from the origin, p = mv is its linear momentum, and denotes the cross product.
The angular momentum of a system of particles (e.g. a rigid body) is the sum of angular momenta of the individual particles. For a rigid body rotating around an axis of symmetry (e.g. the fins of a ceiling fan), the angular momentum can be expressed as the product of the body's moment of inertia I (a measure of an object's resistance to changes in its rotation rate) and its angular velocity ω:

In this way, angular momentum is sometimes described as the rotational analog of linear momentum.
Angular momentum is conserved in a system where there is no net external torque, and its conservation helps explain many diverse phenomena. For example, the increase in rotational speed of a spinning figure skater as the skater's arms are contracted is a consequence of conservation of angular momentum. The very high rotational rates of neutron stars can also be explained in terms of angular momentum conservation. Moreover, angular momentum conservation has numerous applications in physics and engineering (e.g. the gyrocompass).

From what I saw I also know that there are several different Types of Black Holes from spinning Black Holes, Non-Rotating Black Holes, and I think another one but not sure what the name of it is? Or I could just be wrong about all of it.

pzkpfw
2010-Nov-06, 05:16 AM
I understand what everyone is saying ...

If you are going to cite another web site, please acknowledge that. It's best to include a link.
Was this it? http://en.wikipedia.org/wiki/Angular_momentum

...and, what's that quote got to do with the topic?

Gamefreak89
2010-Nov-06, 08:26 AM
Wikipedia doesn't care I do it all the time and I never get in trouble doing it, its free information for everyone of course :D what quote? Are you talking about my signature dude? That has nothing to do with the topic its been like that for over a year and a half now.

Gamefreak89
2010-Nov-06, 08:27 AM
*Face Palms self* What the heck are you talking about? Mod I think you might need to pay closer attention to my posts next time alright? :D

Here maybe this will clear things up next time: http://en.wikipedia.org/wiki/Wikipedia:Copyrights

It says right there its like free software can be used freely without acknowledge from the author as Wikipedia is based around Free Information written by users who join Wikipedia, also I think that warning you gave me was a tad bit excessive don't you think? Plus I would believe that images and certain words or phrases only apply to copyright and with the acknowledgement from the author first. Ok sure next time I'll remember to post the link but most of Wikipedia are written anonymous users all the time.

noncryptic
2010-Nov-06, 09:08 AM
Wikipedia doesn't care I do it all the time and I never get in trouble


It says right there its like free software can be used freely without acknowledge from the author

I think the issue is not whether wiki cares, not is it about acknowledging the author of the wiki article. It's just prudent to acknowledge the source, as to avoid the impression that you are the source, and so that people can independently verify the information.


"A prime purpose of a citation is intellectual honesty; to attribute to other authors the ideas they have previously expressed, rather than give the appearance to the work's readers that the work's authors are the original wellsprings of those ideas."
http://en.wikipedia.org/wiki/Citation

Shaula
2010-Nov-06, 10:20 AM
"A prime purpose of a citation is intellectual honesty; to attribute to other authors the ideas they have previously expressed, rather than give the appearance to the work's readers that the work's authors are the original wellsprings of those ideas."http://en.wikipedia.org/wiki/Citation
And more generally so that we can check the weight we apply to the author of the source. A quote from the website of Mrexenblis the 135th, time travelling high overlord of Darzet in the 34th century, is not going to carry the intellectual weight of a quote from Nature.

Hornblower
2010-Nov-06, 12:15 PM
Can we rule out billions?

A big part bright visible stars we see are OB dwarfs, which are very few in number but bright. Yet they are short lived - under 100 million years. Most of the rest we see are red giants that also are short lived and few in number. Most stars in any defined volume of space, such as Solar neighbourhood are K and M dwarfs, which last longer than the age of world.

But neutron stars and especially black holes last forever. The stars that eventually burn out to black holes do so in under 10 million years, but the world has lasted over 10 milliards of years and all the black holes made over the thousands of generations of stars are still around. Black holes should outnumber O dwarfs thousands of times, even more so if young Milky Way held more O dwarfs than now.

On the other hand, the ratio of M dwarfs to K dwarfs should be unchanged, because even the brightest K0 dwarfs have not yet burnt out.

What is the number ratio of K dwarfs to white dwarf remnants of intermediate mass stars? What is the number ratio of white dwarfs to neutron stars? Neutron stars to black holes?

Red dwarfs have minimum brightness and shine consistently over milliards of years, such that they can be seen in visible. White dwarfs have smaller radiating area, but they cool slowly and the eldest are still at 4000 K, so they can be seen in visible as well. But how can old neutron stars and old black holes be seen?

How much gas would a Population II neutron star be accreting from the Local Bubble interstellar gas passing through at 100 km/s? How about a Population II black hole?

All gravitational energy of accreting gas must be radiated by a neutron star, somewhere in far UV or mild roentgen rays. Are any neutron stars seen in thermal surface radiation that are not pulsars?

A black hole has event horizon instead of surface. So infalling gas may simply carry its energy beyond event horizon instead of radiating it. Or when it misses the event horizon, it can simply pass on the hyperbolic orbit and also radiate nothing. What is theoretical minimum brightness of a black hole that is accreting interstellar gas?

Nowhere in this post do I see any estimate of how many supermassive stars might have existed in our galaxy since the beginning. I have seen many references over the past few decades indicating that roughly one core collapse supernova per galaxy per century is typical of large spirals. That would make something on the order of 100 million remnants, meaning neutron stars and perhaps some black holes, a fairly realistic estimate for our galaxy. At roughly one remnant for every 1000 main sequence stars, that would put them an average of roughly 100 lightyears apart in our region.

Googling "supernovae per century" turned up numerous links in concurrence with my numbers. I do not know right away just how reliable any given one is, but the general agreement is pretty convincing.

By the way, what is a milliard?

AndreasJ
2010-Nov-06, 03:08 PM
By the way, what is a milliard?
A thousand million, the same as an American billion. When milliards are used, a "billion" means a million million.

Strange
2010-Nov-06, 06:32 PM
*Face Palms self* What the heck are you talking about? Mod I think you might need to pay closer attention to my posts next time alright? :D

Here maybe this will clear things up next time: http://en.wikipedia.org/wiki/Wikipedia:Copyrights

It says right there its like free software can be used freely without acknowledge from the author as Wikipedia is based around Free Information written by users who join Wikipedia, also I think that warning you gave me was a tad bit excessive don't you think? Plus I would believe that images and certain words or phrases only apply to copyright and with the acknowledgement from the author first. Ok sure next time I'll remember to post the link but most of Wikipedia are written anonymous users all the time.

I don't really want to continue this sidetrack, but I think this is important (for BAUT and as a more general principle) - it used to be a large part of my job.

I'm not sure you fully understood the copyright page you linked to. In particular you need to read the section on re-use and attribution: http://en.wikipedia.org/wiki/Wikipedia:Copyrights#Reusers.27_rights_and_obligat ions

Gamefreak89
2010-Nov-07, 04:44 AM
Well alright then back to the Black Hole Question I think when Black Holes gobble up matter they grow larger and probably more noticeable right?

astromark
2010-Nov-07, 06:31 AM
That might only be part of the story... Yes, it might be right to say that the mass of the BH increases.

Its gravity effect gets stronger. It might increase in size or just increase its mass. The event horizon would increase as mass increases...

none of those thing make it easy to see... Only the amount of in falling, orbiting objects dust and debris give a clue to the BH location.

As you understand the mass of the BH that is inside the event horizon is never seen. That light image is not getting to you.

Another method of detection is the gravity signature. Other stars are orbiting a large mass object.. Likely a BH gives that clue.

Nereid
2010-Nov-07, 07:12 AM
I had - but I thought it was a (gamma-ray) pulsar.

However, now I found about Magnificent Seven - which, though weakly periodic, do seem to be thermal emitters.

But they, like Geminga, are mere few million years old. How bright would 10+ milliard year old neutron stars be?
Truly isolated ones would likely be extremely faint, in all wavebands.

However, for every truly isolated neutron star, how many would be expected to be a member of a binary? Let's say somewhere between 0.1 and 1. That suggests that we can find nearby old neutron stars by examining all nearby binaries. I suspect, but do not know, that just such searches have been done ...

Also, if an old, singleton neutron star were moving at a decent speed wrt its local ISM, it would leave an observable wake, such as has been seen in the case of {insert examples here; I couldn't find any in a quick search, but I know they exist}.

Nereid
2010-Nov-07, 07:14 AM
Well alright then back to the Black Hole Question I think when Black Holes gobble up matter they grow larger and probably more noticeable right?
It's the gobbling up that is noticeable; unless a stellar mass BH is in a binary, or moving at a fair clip wrt its local ISM, it'd be no more noticeable than one one-tenth its mass, or one with ten times its mass.

Gamefreak89
2010-Nov-07, 07:35 AM
From what I'm guessing the Black Hole causes disturbances in other stars orbits can this also be seen from the telescopes based here on Earth or out in space?

astromark
2010-Nov-07, 07:43 AM
Yes. We have located objects of mass too great for the detected image directly... We have images of Sag.,A.

or images of the field containing Sag.,A. I am still not absolutely clear that we have imaged a black Hole.

We are absolutely sure of the existence of these objects. As the gravity mass is so great only a BH could contain such...

So to lay claim of finding a near to us solar mass Black Hole. Is a indirect science.

That is to say we know of them by the gravity well...we have found.

From memory I recall 'V4641' as a close to us BH. with a companion star binary system... but even I do not trust my memory.

and as a side issue...A mallard is a duck. without the Malarkey... Could we please have a clear description of what value numbers have...

Cross the Atlantic and the billion has a different value.. could someone who understands this please explain... and why.?

AndreasJ
2010-Nov-07, 08:29 AM
From what I'm guessing the Black Hole causes disturbances in other stars orbits can this also be seen from the telescopes based here on Earth or out in space?

Only if it gets quite close.

(It's a common misconception that the gravity of a black hole is particularly strong. It isn't - at a given distance, the pull of a 5 MS black hole is the same as a 5 MS star. What's different is that you can get very close to a black hole without being actually inside it, unlike star, but that's an irrelevant difference when it comes to affecting neighbouring stellar systems.)

astromark
2010-Nov-07, 09:14 AM
AndreasJ; are you simply saying that a five times solar mass black hole has the same mass as a five times solar mass star ?

Why are you thinking orbiting that mass would be any different ? or is it just the way you have said this...? I am a little confused hobbit.

Strange
2010-Nov-07, 09:23 AM
Well alright then back to the Black Hole Question I think when Black Holes gobble up matter they grow larger and probably more noticeable right?

I could be wrong, but I would imagine the mass they absorb after they have been created is usually insignificant compared to their original mass. Unless they happened to be part of a binary system and (eventually) swallow the other star entirely.

Jeff Root
2010-Nov-07, 09:24 AM
Because the distances to stars other than the Sun are so enormous,
the exact positions of the stars are poorly known. So if a star's
position were changed slightly by a passing black hole, chances are
that the effect would not be detected, unless the encounter was
very close and someone happened to be observing with appropriate
equipment right at that moment. If a star had an encounter with a
black hole 200 years ago, there is no way that encounter could be
discovered now (after accounting for light travel time, of course).

Has this been mentioned yet? The faster a black hole is moving
toward us, the less it will perturb the orbits of the planets at a
given distance. The faster they are, the harder they are to find!

-- Jeff, in Minneapolis

speedfreek
2010-Nov-07, 12:48 PM
AndreasJ; are you simply saying that a five times solar mass black hole has the same mass as a five times solar mass star ?

Why are you thinking orbiting that mass would be any different ? or is it just the way you have said this...? I am a little confused hobbit.

I think it is the way he said it! :)

The pull of a 5 MS black hole is the same as a 5 MS star, to anything orbiting that star. If the Sun were a black hole (which it cannot be, as it has too little mass, but let's suspend this rule for the sake of an easy example!) then it would have no effect on the orbit of Earth or the orbit or Mercury. If there were a 1 MS black hole instead of the Sun, you would have to be orbiting at a distance that was originally inside the Sun before you noticed anything different, gravitationally.

If the Sun were a black hole, the event horizon, where the escape velocity is c, would have a radius of only 3 km.

chornedsnorkack
2010-Nov-07, 02:33 PM
Nowhere in this post do I see any estimate of how many supermassive stars might have existed in our galaxy since the beginning. I have seen many references over the past few decades indicating that roughly one core collapse supernova per galaxy per century is typical of large spirals. That would make something on the order of 100 million remnants, meaning neutron stars and perhaps some black holes, a fairly realistic estimate for our galaxy.

Yes, but young Milky Way had a higher rate of supernovae.
The present star formation rate turns out to be about 1 solar mass per year.

Nereid
2010-Nov-07, 02:51 PM
Yes, but young Milky Way had a higher rate of supernovae.
The present star formation rate turns out to be about 1 solar mass per year.
young Milky Way had a higher rate of supernovae

One of the fascinating, yet irritating, things about core collapse supernovae is that we don't yet have a good handle on what proportion end up as neutron stars vs black holes, for a given initial mass. Then there's the uncertainty over the proportion of high-mass stars in binaries which do not end up going supernova because enough mass is transferred to the companion (or lost to the system). Finally, there are environmental effects; how does the state of the natal gas cloud/nascent compact star cluster affect the evolution of high-mass stars?

AFAIK, some bounds can be put on these factors, but the combined result is that neutron star/stellar black hole production rates in the early universe (say, z ~2-5), in galaxies which became MW-like (at z ~0) are poorly constrained indeed.

Of course, I could be quite wrong; I would welcome references to robust, tight estimates of such rates ...

astromark
2010-Nov-07, 07:19 PM
Yes Speedfreek; as I thought.. and I should not have used sol as a unfit example... thanks.

@ Nereid; but we do know the mass requirement for the difference between a neutron star to a black hole a.. ?

We just can not know the effect of near to it companions and mater ? or am I jumping to conclusions.

Asking for more robust data... fair enough... It will come. I doubt you are so wrong...

Gamefreak89
2010-Nov-07, 10:44 PM
Just thinking about Black Holes makes me sick to my stomach sometimes (Maybe its either the food or the thought of one? lol) Sarcastically speaking of course, knowing that if our sun is a 5 Ms (I don't know the exact number for it) and a black hole encounter would be of 2 or possibly 3 Ms would it affect the orbit of our star?

Grey
2010-Nov-07, 11:22 PM
Just thinking about Black Holes makes me sick to my stomach sometimes (Maybe its either the food or the thought of one? lol) Sarcastically speaking of course, knowing that if our sun is a 5 Ms (I don't know the exact number for it) and a black hole encounter would be of 2 or possibly 3 Ms would it affect the orbit of our star?By definition, our Sun is one solar mass. Certainly if a stellar mass black hole came within a reasonably close distance, it would affect the movement of the Sun and the orbits of the planets. The same would be true for a normal star or a neutron star passing by. But it's worthwhile to remember that space is very empty, and stars are pretty unlikely to come close to each other. It's fantastically unlikely for something to come close. You're much more likely to die from a car accident than you are to die because a black hole disrupts the Earth's orbit, sending us all out into deep space to freeze.

Gamefreak89
2010-Nov-08, 03:20 AM
Well I would rather freeze then be sucked up lol if our planet was thrown into a different orbit farther away from where we are now but still orbiting the sun I suppose humans could still survive if a Hole Black did come close to us by a little but not close enough to actually suck us up nor screw with the sun's orbit.

astromark
2010-Nov-08, 06:08 AM
I do not think that the value of 5 Ms means anything that would change this conversation... I do not have the faintest idea what 5 Ms means...?

When talking of stars and there masses we often use 'Solar Masses ' as the yardstick to make comparisons with...

Five solar masses might be written as 5 sm... is that what you speak of ?

Our Sun has one solar mass. It is 332,830 times larger than earth.... that's earth masses.

If you wish to reach escape velocity from a near to Sol location. 619 km/sec is required... from earth its only 11km/sec

and all of that IS relevant when you ask of what might disrupt this solar system... It need not be a BH...

It would be calculable to work out at what distance a solar mass object could destroy this systems equilibrium.

There is a simulation program available that lets you place a object into this solar system and it shows you what would happen...

( Unfortunately I ran and deleted it years ago...) That is what you want to help you with this...

I remember inserting a earth mass object where Mars is... It took just eight years to eject all but mercury..

All eight planets went wobbling off asunder... No collisions or near misses required.

Utter anarchy and in just eight orbits to disrupt it ... fascinating...

neilzero
2010-Nov-08, 09:47 AM
As the others posted, any black holes heading our way will likely miss our sun by a light year or more, although they would be almost that close for several centuries and would disrupt the orbits of the planets significantly. Our sun would also get a new orbit around the galaxy, but that would not matter for millions of years, perhaps much longer. Ms could mean millions of seconds, but that does not clarify the meaning. Neil

Jeff Root
2010-Nov-08, 11:33 AM
Ms is a standard notation for "solar mass", the mass of the Sun.
When subscripts aren't available, or just aren't used, the notation
may simply be "Ms". Which is, indeed, also the symbol for the
SI metric unit "megaseconds".

-- Jeff, in Minneapolis

speedfreek
2010-Nov-08, 07:16 PM
If there were a 1 MS black hole instead of the Sun, you would have to be orbiting at a distance that was originally inside the Sun before you noticed anything different, gravitationally.

Yup. Ms means solar mass! :)

Nereid
2010-Nov-08, 07:26 PM
By definition, our Sun is one solar mass. Certainly if a stellar mass black hole came within a reasonably close distance, it would affect the movement of the Sun and the orbits of the planets. The same would be true for a normal star or a neutron star passing by. But it's worthwhile to remember that space is very empty, and stars are pretty unlikely to come close to each other. It's fantastically unlikely for something to come close. You're much more likely to die from a car accident than you are to die because a black hole disrupts the Earth's orbit, sending us all out into deep space to freeze.
It's probably worth noting that many years' of pulsar observations can be analysed to show that there is no ~Ms object within a few thousand au or so of us (these observations have been used to constrain the existence of ~Jovian-mass objects at distances well beyond the Kuiper Belt; they are just as good at constraining the existence of ~solar-mass objects further away).

If anyone would like a reference or two to these observations, just ask.

Gamefreak89
2010-Nov-08, 08:18 PM
A Black Hole would miss by a light year?! There sure is a lot of empty space out there. I wonder if its possible for a Super Massive Black Hole to be shot out of its own galaxy?

chornedsnorkack
2010-Nov-08, 08:22 PM
However, for every truly isolated neutron star, how many would be expected to be a member of a binary? Let's say somewhere between 0.1 and 1.

Which proportion of observable pulsars are members of binaries?

Nereid
2010-Nov-08, 08:24 PM
A Black Hole would miss by a light year?! There sure is a lot of empty space out there. I wonder if its possible for a Super Massive Black Hole to be shot out of its own galaxy?
I wonder if its possible for a Super Massive Black Hole to be shot out of its own galaxy?

Exceedingly unlikely. Even in galaxy collisions in which the two SMBHs come close to each other, they will radiate so much gravitational wave radiation that an inspiral is all but inevitable (assuming the collision takes place at a sufficiently low mutual speed).

However, if one galaxy in such a collision had a close pair of SMBHs (a close binary) and the other came in with just the right combo of speed and direction, you may get an ejection of one SMBH, just as happens in the core of globular clusters (but with stars, not SMBHs).

Nereid
2010-Nov-08, 08:25 PM
Which proportion of observable pulsars are members of binaries?
Off the top of my head, I don't know ... though I do recall that it's at least 10% ...

Jeff Root
2010-Nov-08, 11:36 PM
Off the top of *my* head, I'd say that ejection of a supermassive
black hole from a galaxy's center is practically impossible, but that
ejection of a stellar-mass black hole (typically several solar masses)
is about as likely as ejection of a neutron star, or an ordinary star
of similar mass. Something that happens occasionally.

-- Jeff, in Minneapolis

JCoyote
2010-Nov-09, 07:25 AM
I would imagine the biggest issue of a SMBH being ejected from its galaxy is the tendency of said SMBH to drag the galaxy along with it. LOL

I have a project that's been sitting on the shelf for a while but part of the initial concept involved a black hole entering the solar system at very high velocity. Even in this case it allowed Earth about 500 years of preparation, for all the good it did.

I personally lean toward having Earth plunge into a BH instead of flinging out into the cold. I don't like the slow death, I'd rather take a whole civilization on a relativistic roller coaster ride!

Nereid
2010-Nov-09, 07:33 AM
I would imagine the biggest issue of a SMBH being ejected from its galaxy is the tendency of said SMBH to drag the galaxy along with it. LOL [...]
A SMBH's mass is a tiny fraction of the mass of the galaxy it is the central object of the nucleus of; while it may well take much of the matter in the nucleus with it (most galactic nuclei contain at least one quite rich, compact star cluster, for example), it won't have any particularly significant effect on the rest of the galaxy.

JCoyote
2010-Nov-09, 07:36 AM
A SMBH's mass is a tiny fraction of the mass of the galaxy it is the central object of the nucleus of; while it may well take much of the matter in the nucleus with it (most galactic nuclei contain at least one quite rich, compact star cluster, for example), it won't have any particularly significant effect on the rest of the galaxy.

You'd think there was a reason I put LOL in there. ;)

Gamefreak89
2010-Nov-09, 07:58 AM
I would imagine the biggest issue of a SMBH being ejected from its galaxy is the tendency of said SMBH to drag the galaxy along with it. LOL

I have a project that's been sitting on the shelf for a while but part of the initial concept involved a black hole entering the solar system at very high velocity. Even in this case it allowed Earth about 500 years of preparation, for all the good it did.

I personally lean toward having Earth plunge into a BH instead of flinging out into the cold. I don't like the slow death, I'd rather take a whole civilization on a relativistic roller coaster ride!

500 years?! by then humans should be long gone from the planet unless we are stay at a type 1 civilization and we haven't even came close to that point, a type 2 civilization takes about 500 to 1000 years to actually become one but then again If we were far ahead in that time period I wouldn't be wanting to sit around here on Earth lol. But in any even if Earth and its inhabitants do become in dangered in the near future I'm pretty sure we would figure something out. Like I don't know abandon the planet and leave everyone behind :D. On another note SMBH's being shot out galaxy is kind of neat and scary in some ways. I wonder if its possible to take a picture of one with our satellites?

JCoyote
2010-Nov-09, 09:43 AM
I am always amazed with people assuming it's easy to take a picture of a black hole.

Also I think you are over assuming the real world possibilities of moving that many people sans a lightspeed workaround. I do assume a lightspeed workaround developed, but even then... a hundred or so years worth of ship making does not mean you can get everyone off planet. You have to have somewhere to PUT them before you can evacuate everyone.

There is nothing to do but run. And in this case only take a handful of humans. And finding another planet comparable enough to Earth? That's where it gets tough.

That's getting off subject though. The only ways to see black holes are by the matter they consume producing by-product reactions. No gases crushing into tight areas at high velocities, and you don't have much to see them with other than an odd transient gravitational lens effect that would be likely blamed on optics or atmosphere or any number of things. A black hole would have to be VERY close to our system to disturb orbits, I agree a heightened incidence of comets might be the only clue.

Gamefreak89
2010-Nov-09, 10:54 AM
So I'm guessing one shouldn't be worrying about such things as there are other threats out there far more closer to home? Am I right? Like Asteroids, comets, super volcanoes and what not I guess. Also Since this Earth has been here for Billions of years and us humans have been here for a short period of time but not to go off topic.

Anyways talking about BH's always makes me sick to me stomach sometimes kind of have a fear of them lol.

Grey
2010-Nov-09, 06:01 PM
So I'm guessing one shouldn't be worrying about such things as there are other threats out there far more closer to home? Am I right? Like Asteroids, comets, super volcanoes and what not I guess.Absolutely. Not to mention heart attacks, car accidents (and other kinds of accidents, too), stroke, pneumonia, and a whole array of other things that are much more likely to be the reason that you die than any of the things on your list. And some of them, you can even do something about, or at least lower the odds.


Anyways talking about BH's always makes me sick to me stomach sometimes kind of have a fear of them lol.Remain calm! There are no nearby black holes on a collision course to swallow the Earth within your lifetime. That would still be true if some miraculous medical advance lets you live to be a couple thousand years old. Enjoy the beauty of the universe, and the wonder of discovering how it works.

Spoons
2010-Nov-11, 06:09 AM
What you really should be worried about is those super-intelligent army birds that recently escaped and are said to be gorging on human flesh while the people sleep. That's a much bigger risk to you than black holes. :shifty:

Oh, and I may have confused your words, gamefreak, but we're a Type 0 civilisation, not a Type 1.

slang
2010-Nov-11, 08:12 AM
It's probably worth noting that many years' of pulsar observations can be analysed to show that there is no ~Ms object within a few thousand au or so of us (these observations have been used to constrain the existence of ~Jovian-mass objects at distances well beyond the Kuiper Belt; they are just as good at constraining the existence of ~solar-mass objects further away).

If anyone would like a reference or two to these observations, just ask.

That sounds pretty clever.. how does that work?

ETA: thought of something: absence of expected Shapiro delays?

Nereid
2010-Nov-11, 09:32 AM
That sounds pretty clever.. how does that work?

ETA: thought of something: absence of expected Shapiro delays?
The timing of pulses from pulsars is the key; think of them as distant clocks. If the receivers (radio telescopes at various places on the Earth's surface) detect changes in that timing (which they do), one can develop a model for them. That model will include the motion of the receivers wrt the solar system barycentre. If the motion is different that what you'd expect from that caused by the known masses (and their positions etc) in the solar system, then there will be an unmodelled acceleration. No such has been found.

This recent paper (http://arxiv.org/abs/1008.3607) (preprint actually) provides a good account (though the application is planetary system masses); and this one (http://arxiv.org/abs/astro-ph/0506548)'s abstract gives a concise summary:

Many astronomers have speculated that the solar system contains undiscovered massive planets or a distant stellar companion. The acceleration of the solar system barycenter can constrain the mass and position of the putative companion. In this paper we use the most recent timing data on accurate astronomical clocks (millisecond pulsars, pulsars in binary systems and pulsating white dwarfs) to constrain this acceleration. No evidence for non-zero acceleration has been found; the typical sensitivity achieved by our method is a/c=a few times 10^{-19} s^{-1}, comparable to the acceleration due to a Jupiter-mass planet at 200 AU. The acceleration method is limited by the uncertainties in the distances and by the timing precision for pulsars in binary systems, and by the intrinsic distribution of the period derivatives for millisecond pulsars. Timing data provide stronger constraints than residuals in the motions of comets or planets if the distance to the companion exceeds a few hundred AU. The acceleration method is also more sensitive to the presence of a distant companion (> 300-400 AU) than existing optical and infrared surveys. We outline the differences between the effects of the peculiar acceleration of the solar system and the background of gravitational waves on high-precision timing.

ETA: here (http://www.centauri-dreams.org/?p=14050) is a one-page popular account of the method.

mikeg64
2010-Nov-11, 11:29 AM
I thought the nearest black hole to earth was Cygnus X-1 the famous X-ray source which is about 6000 light years away. After checking details on wikipedia its mass is estimated at 8.7 Solar masses and it forms part of a binary system, its partner is blue supergiant variable.

However after an outburst in 1999, V4641 Sagittarii revealed itself to be the nearest black hole at around 1600 light years away. Further investigations have indicated that it may be 15 times further away than this!

It's a really interesting object being dubbed a micro quasar imagery allegedly indicates superliminal X-ray jets, most disturbing!

It's not so far to our nearest time machine after all!

Grey
2010-Nov-11, 06:04 PM
It's not so far to our nearest time machine after all!You have a different distance gauge than I do if 1600 light years is "not so far". ;)

chornedsnorkack
2010-Nov-11, 07:31 PM
As far as the probability of Solar System colliding with a black hole is concerned: the nearest star is at 4 ly, passing us at 2 ly or so over a few tens of thousands of year. If, say, the closest approach of any star in a million years is at 1 ly (63 000 au) then in all probability the closest approach of any star in 10 milliard year lifetime of the Sun would be 0,01 ly (630 au).

And black holes are by far outnumbered by red dwarfs.


No evidence for non-zero acceleration has been found;
Does Sun orbit the Milky Way?

Gamefreak89
2010-Nov-11, 08:53 PM
As far as the probability of Solar System colliding with a black hole is concerned: the nearest star is at 4 ly, passing us at 2 ly or so over a few tens of thousands of year. If, say, the closest approach of any star in a million years is at 1 ly (63 000 au) then in all probability the closest approach of any star in 10 milliard year lifetime of the Sun would be 0,01 ly (630 au).

And black holes are by far outnumbered by red dwarfs.


Does Sun orbit the Milky Way?

10 milliard year is what 10,000 years or somethin? and as far as AU's go how can one be sure that the exact distance is right? I'm sure the Kuiper belt is half a light year out and the Oort Cloud is abotu 1 1/2 of a light year from us. Using that estimate any close approach from a BH or another star such as a Red Dwarf (Which I believe as a smaller mass than our sun) would take 10's of thousands to 1 million years if it comes with in 2 light years. Also knowing that BH's travel at 100 to 300 M/s (Miles per second) it would umm..... Darn it my brain can't work all of this out and I can't use google either because I wouldn't know what to type in lol.

slang
2010-Nov-11, 09:06 PM
The timing of pulses from pulsars is the key; think of them as distant clocks. If the receivers (radio telescopes at various places on the Earth's surface) detect changes in that timing (which they do), one can develop a model for them. That model will include the motion of the receivers wrt the solar system barycentre. If the motion is different that what you'd expect from that caused by the known masses (and their positions etc) in the solar system, then there will be an unmodelled acceleration. No such has been found.

Thanks Nereid, for me that's quite a bit to chew on, even just going by the intros and conclusions. I think I now understand the method at least. Clever indeed, and it's telling that even the location of the observatory on Earth must be taken into account, for measuring stuff coming from many light years away.

AndreasJ
2010-Nov-11, 09:31 PM
10 milliard year is what 10,000 years or somethin?
1 milliard = 1 (American) billion = 1 000 000 000 = 109

and as far as AU's go how can one be sure that the exact distance is right? I'm sure the Kuiper belt is half a light year out and the Oort Cloud is abotu 1 1/2 of a light year from us.
The Kuiper belt is 30-50 AU out. (Half a light year is about 30 thousand AU.) The outer limit of the Oort Cloud may indeed be at around 1 light years (~100 000 AU).

Strange
2010-Nov-11, 09:38 PM
10 milliard year is what 10,000 years or somethin? and as far as AU's go how can one be sure that the exact distance is right? I'm sure the Kuiper belt is half a light year out and the Oort Cloud is abotu 1 1/2 of a light year from us. Using that estimate any close approach from a BH or another star such as a Red Dwarf (Which I believe as a smaller mass than our sun) would take 10's of thousands to 1 million years if it comes with in 2 light years. Also knowing that BH's travel at 100 to 300 M/s (Miles per second) it would umm..... Darn it my brain can't work all of this out and I can't use google either because I wouldn't know what to type in lol.

A milliard is 1,000,000,000 - it is used to avoid the ambiguity of "billion".

The kuiper belt is about 0.0005 light years away.

The Oort cloud is about 0.8 ly.

(By the way, if you type something like 30 light years / 300 miles per second in fortnights into google it will do the math for you)

Gamefreak89
2010-Nov-12, 04:56 AM
So I'm guessing that the first signs of a Black Hole like one of you said was "An Increase in the number of Comets", disturbances in the planet's orbit starting with Neptune, then working its way down to Jupiter and so on. I wonder what would happen if Jupiter got slung out its orbit by a Black Hole? Or for that matter what would it look like?

Jens
2010-Nov-12, 10:46 AM
So I'm guessing one shouldn't be worrying about such things as there are other threats out there far more closer to home? Am I right? Like Asteroids, comets, super volcanoes and what not I guess. Also Since this Earth has been here for Billions of years and us humans have been here for a short period of time but not to go off topic.

Anyways talking about BH's always makes me sick to me stomach sometimes kind of have a fear of them lol.

Yes, as Grey said, there are lots of other things, like angry people, reckless drivers, cancer, stroke, and heart attacks, that have a realistic chance of killing you. Actually, worrying about black holes is almost certainly more deleterious to your health than a black hole will ever be. If it causes you to lose sleep, it will drive up your blood pressure.

Plus, what's so bad about being sucked into a black hole? Would you rather die in a car accident or in a house fire or from lung cancer? I don't think it would be any less pleasant.

Jeff Root
2010-Nov-12, 01:10 PM
So I'm guessing that the first signs of a Black Hole like one of you
said was "An Increase in the number of Comets",
No, disturbed comets would almost always take longer to reach
the inner Solar System than the black hole itself would. The
reason comets can be easily sent toward the inner Solar System
is that they are so far from the Sun that only a very small change
in speed is needed to lower their perihelia into the inner Solar
System. If a black hole interacts with comets at a great distance
(several AUs), that can happen. Then the comets fall toward the
Sun, starting out moving very, very slowly (even slower than their
usual orbital speed).

If a black hole interacts with a comet at a short distance (say, a
few million miles or less), then the comet's speed will change
radically, and it will be flung off in some random direction-- maybe
toward the Sun, but far more likely in some direction not toward
the Sun.

Comets in the Oort cloud are scattered very sparsely. A black hole
might pass through the Oort cloud with no comet encounters closer
than a million miles. So the black hole would almost certainly get
here before any comets did.

-- Jeff, in Minneapolis

Gamefreak89
2010-Nov-13, 01:17 PM
Well do believe Jens has a point though about being sucked into one who knows maybe its a whole lot more pleasant than getting hit by a gamma ray burst? :D

chornedsnorkack
2010-Nov-13, 01:36 PM
If a black hole interacts with a comet at a short distance (say, a
few million miles or less), then the comet's speed will change
radically, and it will be flung off in some random direction-- maybe
toward the Sun, but far more likely in some direction not toward
the Sun.

Comets in the Oort cloud are scattered very sparsely. A black hole
might pass through the Oort cloud with no comet encounters closer
than a million miles. So the black hole would almost certainly get
here before any comets did.

Most comets get into the inner Solar System long after the black hole. But the few comets near the path of the black hole will be scattered ahead of the hole, with speed relative to Sun twice that of the black hole relative to Sun. So they will arrive first.

Jeff Root
2010-Nov-13, 02:37 PM
Yes, they will arrive first, but there will probably be zero of them,
so not a large enough sample to determine that they have a
common origin in a recent perturbation event. :)

-- Jeff, in Minneapolis

grant hutchison
2010-Nov-13, 02:52 PM
Well do believe Jens has a point though about being sucked into one who knows maybe its a whole lot more pleasant than getting hit by a gamma ray burst? :DBeing personally sucked into a black hole would be a painless way to die, assuming you were issued with some sort of spacesuit to prevent your dying in vacuum en route, and assuming there was no accretion disc to enliven your approach. If you fall freely into a black hole from a large distance, tidal forces will destroy you so rapidly, during the last moment of your approach, that you won't have a chance to register any pain.

Grant Hutchison

Jens
2010-Nov-13, 02:59 PM
Being personally sucked into a black hole would be a painless way to die, assuming you were issued with some sort of spacesuit to prevent your dying in vacuum en route...

But even there, I assume that dying from a ruptured spacesuit is a lot more pleasant than dying of lung cancer or some similar illness. Somehow, 15 seconds of breathlessness and fading consciousness seems quite preferable to a lot of the alternatives.

Jeff Root
2010-Nov-13, 11:07 PM
You giuys are totally missing the point. I would rather be tortured for
twenty years by angry fire ants all over my body, than killed instantly
by a black hole, if the Earth is made uninhabiltable by it. I don't see
that Gamefreak was concerned about the end of his own life.

I'd much rather that Earth be nudged out of orbit than swallowed up.
"Cold good."

We just got the first snowfall of the season here. Looks like about
3 or 4 inches of the atmosphere piled up on the ground. When it gets
to be 3 or 4 miles, people will still be here.

-- Jeff, in Minneapolis

grant hutchison
2010-Nov-13, 11:37 PM
You giuys are totally missing the point.Not missing the point, just talking about something else. Hence my use of the adverb "personally".

Grant Hutchison

Gamefreak89
2010-Nov-14, 03:51 PM
You giuys are totally missing the point. I would rather be tortured for
twenty years by angry fire ants all over my body, than killed instantly
by a black hole, if the Earth is made uninhabiltable by it. I don't see
that Gamefreak was concerned about the end of his own life.

I'd much rather that Earth be nudged out of orbit than swallowed up.
"Cold good."

We just got the first snowfall of the season here. Looks like about
3 or 4 inches of the atmosphere piled up on the ground. When it gets
to be 3 or 4 miles, people will still be here.

-- Jeff, in Minneapolis

Good point I can deal with the cold at least we would still be alive and considering the fact that we can always find a way to heat ourselves up.

Wales
2010-Nov-14, 04:25 PM
I'm still waiting for my post to appear with links to papers that "apparently" mathematically refute Black Holes altogether ...

Spoons
2010-Nov-15, 06:54 AM
If it's got links you'll just need to wait a little while for the moderators to get a chance to review it - an anti-spam measure.

It shouldn't be a heck of a lot longer - the Europe mods will probably be online now or soon.

What did this article say about the alternative reason for such fast motion of starts near the centre of the galaxy, or did they not deal with this problem that would be created if you didn't have black holes?

astromark
2010-Nov-15, 09:37 AM
Firstly I would argue that having earth thrown out in the cold would be a horrid way to perish... As earth moved away from the sun... oceans freeze. Atmosphere collapses and we die. freezing or starving and with no water available. I too would prefer the swift death a collision or impactor would deliver... Talking of the end of humanity if the solar earth balance were to be changed... There could be no surviving a out of the goldilocks zone...
As for the question of black holes... Its the gravity mass that gives away the presence of mass. Astronomers might yet need to tweak findings yet.
That is the nature of science. I would not be to quick to disqualify the black hole... Observations of motion and mass have lead us to this point.

Grey
2010-Nov-15, 03:28 PM
You giuys are totally missing the point. I would rather be tortured for
twenty years by angry fire ants all over my body, than killed instantly
by a black hole, if the Earth is made uninhabiltable by it. I don't see
that Gamefreak was concerned about the end of his own life.Well, my point at least was not that getting sucked into a black hole isn't that bad. My point was that it's so fantastically unlikely that a black hole (or any other massive object) would come close enough to have any effect on us that it's hard to comprehend just how small the possibility is, and we can be reasonably certain (from observations like the one Nereid linked to) that there are no large black holes headed our way any time in the next few thousand years at least. So it's not that you shouldn't worry about it because it wouldn't be that bad. It's that you shouldn't worry about it because it's not going to happen.

It can be fun to speculate about what would happen if it did, but if it's making Gamefreak89 feel physically ill, then I think it would be a good idea to remember just how empty space is and just how rare collisions between stars are. Imagine that someone set out some bowling balls for you to find, and you're walking around the countryside looking for them. When you realize that the bowling balls are typically about 4,000 to 10,000 miles apart, and that your speed is limited to about 5 inches per hour (that's the equivalent of about 220 km/sec when we scale down the stars and the distance between them to this size), you'll realize just how rare it is for stars (or the remnants of stars, like black holes) to ever encounter each other.

Even when entire galaxies collide, completely altering the shape of the galaxies involved (my personal favorite example is "the Mice" (http://imgsrc.hubblesite.org/hu/db/images/hs-2002-11-h-full_jpg.jpg)), there would be just a handful of stars that get close enough to really affect each other. The vast majority of stars would just pass right by each other, with their planetary systems (if any) intact, never getting closer than a couple light years.

Gamefreak89
2010-Nov-15, 10:58 PM
Hey is anyone sure about any near by black holes because I read a thread in this section about a NASA news conference can anyone reasure.... I mean confirm this?

Hornblower
2010-Nov-15, 11:05 PM
Hey is anyone sure about any near by black holes because I read a thread in this section about a NASA news conference can anyone reasure.... I mean confirm this?Can you post a link?

Strange
2010-Nov-15, 11:10 PM
I assume this one: http://www.bautforum.com/showthread.php/109357-NASA-news-conference-on-quot-exceptional-object-quot

It is about 50 million light years away, in another galxay far, far away....

slang
2010-Nov-15, 11:15 PM
As it is the thread currently right below this one, I'll presume he means: NASA news conference on "exceptional object" (http://www.bautforum.com/showthread.php/109357-NASA-news-conference-on-quot-exceptional-object-quot)

Chandra news site: (http://www.nasa.gov/mission_pages/chandra/news/H-10-299.html)


The 30-year-old object is a remnant of SN 1979C, a supernova in the galaxy M100 approximately 50 million light years from Earth.

(bold mine) Gamefreak89: In astronomy "nearby" has a somewhat different meaning than when we talk about a trip to the chemist's down the road. Astronomical nearby is usually still very, very, very, very far away in human terms.

Hornblower
2010-Nov-15, 11:17 PM
Thanks for the link. Like a dummy I had forgotten that it was on the same page as this thread.

I would say confidently that there is no significant chance of a close encounter with this object.

Gamefreak89
2010-Nov-16, 12:49 AM
Sorry I jump to conclusions to quickly lol I remember reading one time about a star orbiting a BH but the odd thing is that the star itself was able to escape the gravitational pull of the BH somehow... I can't remember where I read it at I know that it was some article.

slang
2010-Nov-16, 01:07 AM
I remember reading one time about a star orbiting a BH but the odd thing is that the star itself was able to escape the gravitational pull of the BH somehow...

Well, a black hole isn't magic. It's "just" gravity. Only when you get pretty close to a black hole does the behavior become different than say a star or planet (keeping in mind that "pretty close" can be a big range of distances, depending on how massive the black hole is). It certainly doesn't "suck in" everything even remotely in its neighborhood. Try this page from the Phil Plait (and remember it's entirely fictional, our sun cannot become a black hole) : What if the sun collapses into a black hole? (http://www.badastronomy.com/bad/misc/black_hole_sun.html)

Incidentally, here is Phil's blog entry about the discovery in that other thread: Astronomers may have found youngest black hole (http://blogs.discovermagazine.com/badastronomy/2010/11/15/astronomers-may-have-found-youngest-black-hole/).

Gamefreak89
2010-Nov-16, 01:42 AM
Well, a black hole isn't magic. It's "just" gravity. Only when you get pretty close to a black hole does the behavior become different than say a star or planet (keeping in mind that "pretty close" can be a big range of distances, depending on how massive the black hole is). It certainly doesn't "suck in" everything even remotely in its neighborhood. Try this page from the Phil Plait (and remember it's entirely fictional, our sun cannot become a black hole) : What if the sun collapses into a black hole? (http://www.badastronomy.com/bad/misc/black_hole_sun.html)

Incidentally, here is Phil's blog entry about the discovery in that other thread: Astronomers may have found youngest black hole (http://blogs.discovermagazine.com/badastronomy/2010/11/15/astronomers-may-have-found-youngest-black-hole/).

Yeah I know that was all all over the news on the website space home page and NASA as well, there is of course another question I want to ask about a BH the argument between Stephen Hawkings and some other guy (I can't remember his name) they argued about the information paradox and seeing someone fall into a BH from your perspective and vice versa.

Spoons
2010-Nov-16, 10:32 AM
What specifically about that did you wish to ask about?

Grey
2010-Nov-16, 01:59 PM
You're probably thinking about this (http://en.wikipedia.org/wiki/Thorne%E2%80%93Hawking%E2%80%93Preskill_bet) bet with Kip Thorne. Hawking conceded the bet about information, but much of the rest of the physics community remains unconvinced, actually. What's your question about it?

Gamefreak89
2010-Nov-16, 02:47 PM
Well my question is does anyone believe information is lost in a BH?

Grey
2010-Nov-16, 03:12 PM
Well my question is does anyone believe information is lost in a BH?Stephen Hawking thinks the answer is no. Many other physicists think yes. Still others think the question isn't settled. I'm in that last group. I do think we have enough solid data to support that idea that black holes really exist, and that they behave largely as general relativity suggests they should. However, black holes are a fairly extreme case, and we just don't have a lot of solid data for them (no pun intended). When the brightest minds who have studied the subject can't even agree what the correct answer is based on our theoretical models, I don't think we can answer the question with much certainty. We'd probably need to be able to manufacture tiny black holes and study them to be able to know for sure.

slang
2010-Nov-16, 03:40 PM
Well my question is does anyone believe information is lost in a BH?

I don't know if I have even a vague understanding of what, exactly, Thorne and Hawking mean when they talk about information in this context. I suspect it is not quite the same thing as when I, as a computer guy, talk about information.

Grey
2010-Nov-16, 05:33 PM
I don't know if I have even a vague understanding of what, exactly, Thorne and Hawking mean when they talk about information in this context. I suspect it is not quite the same thing as when I, as a computer guy, talk about information.Take a look here (http://math.ucr.edu/home/baez/week207.html) (which gives the full transcript of Hawking's presentation where he concedes the bet), here (http://en.wikipedia.org/wiki/Black_hole_information_paradox) (which give a summary of the whole black hole information paradox issue), and here (http://en.wikipedia.org/wiki/Physical_information) (which talks about what physicists mean when they use the term "information").

Gamefreak89
2010-Nov-16, 07:23 PM
Sounds good I'll read it when I can lol anyways BH's sure are mysterious aren't they? (Not in a magical way but in a Mysterious way on like how giant stars form into BH's).

slang
2010-Nov-16, 07:24 PM
Take a look here (http://math.ucr.edu/home/baez/week207.html) (which gives the full transcript of Hawking's presentation where he concedes the bet), here (http://en.wikipedia.org/wiki/Black_hole_information_paradox) (which give a summary of the whole black hole information paradox issue), and here (http://en.wikipedia.org/wiki/Physical_information) (which talks about what physicists mean when they use the term "information").

Thank you. Tough material, but I think I got enough to see that I would need a good understanding of both quantum physics and general relativity to even dream of asking a meaningful question about the black hole information paradox, or rather, to have an informed opinion on the matter.

astromark
2010-Nov-16, 08:01 PM
I am not a Phd or Master of my own mind even... Lol:) but can formulate in my own mind conclusions of what I see as logical conclusions...
These conclusions are based on a lifetime of science based observation and discussion... ongoing always.
That a object of some five times the solar mass would have after shedding the balance of its hydrogen a gravity well that exceeds the speed of light.
That five times the solar mass.. ( needs checking )... but you will I trust understand my intent.
There is NO reason why a planetary system could not orbit indefinitely such a object...
Stars are orbiting black holes. Binaries and multiples are on record.
Unfortunately the end of a stars life is often a violent and explosive event.
"NOVA" are generally un supportive of stable life bearing environments.
Our view from a safe distance is a very good yardstick...

The original question regarding the nearest to us Black Hole.... Yes, The OP.
In Our neighbourly... vicinity... Closer than the galactic core... where,? how far ? how big ? and what direction is it moving..?

Grey
2010-Nov-16, 09:35 PM
Thank you. Tough material, but I think I got enough to see that I would need a good understanding of both quantum physics and general relativity to even dream of asking a meaningful question about the black hole information paradox, or rather, to have an informed opinion on the matter.Hey, if Stephen Hawking and Kip Thorne can't agree on the answer, we little folk can feel secure in not being too sure about it either. ;)

Jeff Root
2010-Nov-17, 06:48 AM
My impression is that the whole idea of information (with regard to
black holes or anything else) is pure mathematics, and has nothing
to do with physics, even if both the mathematicians and physicists
think it does. If so, then the question of whether information is lost
in a black hole could not be answered even if unlimited numbers of
black holes were at hand to experiment on.

-- Jeff, in Minneapolis

Grey
2010-Nov-17, 02:54 PM
My impression is that the whole idea of information (with regard to
black holes or anything else) is pure mathematics, and has nothing
to do with physics, even if both the mathematicians and physicists
think it does. If so, then the question of whether information is lost
in a black hole could not be answered even if unlimited numbers of
black holes were at hand to experiment on.I would disagree. For example, I think that some of the things that would be included in the category of "information" would be things like baryon number or lepton number, which appear to be conserved in interactions. If a black hole really causes information to be lost, then the number of baryons that you put in to make a black hole might be different than the number of baryons you get back out if it evaporates by Hawking radiation. That would be a testable (well, in principle anyway) experimental result.

Jeff Root
2010-Nov-17, 10:01 PM
Whether information is lost or not, the number of baryons coming
out via Hawking radiation wouldn't be related to the number of
baryons that went in, unless there is a mechanism to make them
be the same. Conservation of baryon number does not provide
such a mechanism.

-- Jeff, in Minneapolis

grant hutchison
2010-Nov-17, 10:32 PM
Whether information is lost or not, the number of baryons coming
out via Hawking radiation wouldn't be related to the number of
baryons that went in, unless there is a mechanism to make them
be the same. Conservation of baryon number does not provide
such a mechanism.Conservation of information, as described by Susskind and others, provides the mechanism to conserve baryon number; whereas information loss into the singularity doesn't.

Grant Hutchison

Gamefreak89
2010-Nov-18, 05:13 PM
Does the laws of Thermodynamics come in to play?

Grey
2010-Nov-18, 07:33 PM
Whether information is lost or not, the number of baryons coming
out via Hawking radiation wouldn't be related to the number of
baryons that went in, unless there is a mechanism to make them
be the same. Conservation of baryon number does not provide
such a mechanism.I agree with grant. This is just the kind of question that's being asked when physicists speculate about whether information is lost in a black hole or not. It's not just arbitrary mathematics, there are hypothetically different results depending on what the answer is, even if the experiments to test those results aren't things that we could do in the foreseeable future.

Gamefreak89
2010-Nov-22, 12:53 AM
So how is information retrieved from a BH then? Or better yet what happens to the information in a BH?

slang
2010-Nov-22, 07:49 AM
So how is information retrieved from a BH then? Or better yet what happens to the information in a BH?

I'm not sure what kind of answer you expect. It isn't like you feed the BH a copy of Encyclopedia Britannica and extract a few words. AIUI, the information paradox is to do with which types of subatomic particles and energy fall into the BH, and in which way or form they may or may not radiate from the BH as Hawking Radiation.

Grey
2010-Nov-22, 01:56 PM
So how is information retrieved from a BH then? Or better yet what happens to the information in a BH?We don't know. And the experts (brilliant physicists who have spent much of their careers focusing on studying black holes both through theoretical models and observations) don't agree, as I noted above. So we really don't know.

Gamefreak89
2010-Nov-28, 08:43 AM
Ok so is it possible to create a stable Black Hole with todays current technology? So that we can observe it.

Shaula
2010-Nov-28, 11:06 AM
Nope. Stable = large for black holes. Some theories suggest that particle colliders will soon be able to make micro black holes but they will decay very fast. To make anything like a stable one you'd need to compress planet magnitude amounts of matter into a sphere a few km or even m across. And you have the problem of disposal - a black hole is not just for Xmas. Once made you have to keep feeding it (tiny amounts but still a bit) basically forever or else eventually ... Boom. We are talking silly amounts of time here so to be fair that might be the least of our worries! I think (quick Google) that the lifetime is thought to be M^3 /3.4e15. So a kilogram of black hole goes bang in order of 10e-14s, 1 kilotonne of black hole in 5 minutes, one megatonne in 10,000 years. So you'd need something like a few thousand (call it ten for safety) tonnes of matter jammed down into a sphere (radius is roughly 3M/Ms) smaller than an atomic nucleus... You could make it 'easier' by using more matter but it is still way, way beyond us.

Gamefreak89
2010-Nov-28, 11:51 AM
So we are talking technology possibly within a time range of 50 to 75 years? You know I also thought of something else to instead of doing it here on Earth they do those kind of projects on Mars or some other planet or moon out in the solar system but hey that is just my opinion.

antoniseb
2010-Nov-28, 01:27 PM
So we are talking technology possibly within a time range of 50 to 75 years? ...
I think that's pretty optimistic about the rate of advance of our technology. I'd be surprised if such a thing were possible within a thousand years.
BTW, this is a bit off the original topic. Do you want to separate the threads?

neilzero
2010-Nov-28, 02:48 PM
~Hi Shaula/forgive me for editing. Some numbers are much appreciated, and I hope I did not edit erroneously~ Some theories suggest that particle colliders will soon be able to make micro black holes but they will decay very fast. To make anything like a stable one you'd need to compress planet magnitude amounts of matter into a sphere a few km or even m across.~lots more matter is needed to make even a one meter black hole~ And you have the problem of disposal - a black hole is not just for Xmas. Once made, you have to keep feeding it ~kilogram amounts or more~ basically forever or else eventually ~gigaton of TNT size boom. We are talking silly amounts of time here so to be fair that might be the least of our worries! I think (quick Google) that the lifetime is thought to be M^3 /3.4e15. So a kilogram of black hole goes bang in order of 10e-14s, 1 kilotonne of black hole in 10 microseconds, one megatonne in 10,000 seconds ~if my arithmetic is more correct than yours~ So you'd need something like a few thousand (call it ten for safety) tonnes of matter jammed down into a sphere (radius is roughly 3M/Ms ~what do the letters mean?~) smaller than an atomic nucleus... You could make it 'easier' by using more matter but it is still way, way beyond us. ~Feeding kilograms per second into a sphere smaller than an atomic radius is likely almost impossible. Neil~

Shaula
2010-Nov-28, 03:52 PM
@neilzero
No problems - I was doing very quick and back of envelope stuff to give a flavour of the issues.

A lunar mass black hole is still only about 0.1mm in diameter... So when you say you need a lot more mass to make a 1m black hole you mean a LOT more! Inverting the equation we get M = Ms/3. For M = 1 we get a third of a solar mass of material (10e30kg) to make a one metre black hole... You are perfectly right about feeding rates - very small black holes are effectively impossible to feed and keep stable. I have no idea where the feeding rate vs emission rate falls in an artificial system. It is a few solar masses in the wild IIRC?

So 50-75 years? I'd say no. Barring some amazing discovery that changes everything.

kamaz
2010-Nov-28, 05:03 PM
My impression is that the whole idea of information (with regard to
black holes or anything else) is pure mathematics, and has nothing
to do with physics,

That's not the case. There is an interest in so-called reversible computing, precisely because it has been shown that information loss in combinational logic circuits causes heat dissipation: http://strangepaths.com/reversible-computation/2008/01/20/en/

In fact, we're reasonably close to building single-electron gates, so the effect should be demonstrated experimentally in a few years.

eburacum45
2010-Nov-28, 08:48 PM
So we are talking technology possibly within a time range of 50 to 75 years?

This may be off-topic, but perhaps I can help you there. A fictional project to create a black hole has been mapped out in some detail by C. Sanford Lowe and G. David Nordley. This project would create a black hole with a mass of a billion tonnes, which would be stable on a long time-scale.
You can read about this project here
http://www.gdnordley.com/_files/BHP_Glossary.html
and here
http://www.gdnordley.com/_files/_KL_images/BHP_Architecture.html
and here
http://www.gdnordley.com/_files/_KL_images/BHP_timeline.html

this project involves firing billion ton pellets at each other from a distance of several light years at relativistic speeds, and would require hundreds of years of effort. So not a near-term project.

Gamefreak89
2010-Nov-29, 07:30 AM
So is that right well to stay on topic what exactly is in the middle of black hole? That singularity what does it really look like?

Shaula
2010-Nov-29, 08:03 AM
No one knows. A singularity is where our models break down - in essence it is where GR and QM say "dunno". Maybe there is a degeneracy pressure that allows some form of structured matter to exist, maybe not. We really need a theory of quantum gravity to even start to address that problem.

Gamefreak89
2010-Nov-29, 04:27 PM
Well hopefully in the future we might be able to do so I guess... Another question with the laws of physics how and why does a Black hole actually form? Also what came first the SMB or the Galaxy?

Shaula
2010-Nov-29, 06:24 PM
Well hopefully in the future we might be able to do so I guess... Another question with the laws of physics how and why does a Black hole actually form? Also what came first the SMB or the Galaxy?
How and why the Black hole forms: Usually supernovae. Essentially the remnant core of a very large star at the end of its life is so massive that it cannot hold itself up. First it collapses into neutrons (protons and electrons combining) and if the mass is high enough that the gravity of the body is stronger than the forces holding the neutrons apart then it collapses further. Into something we don't fully understand but have some ideas about - a black hole. Wikipedia has some good articles that introduce the basics of a black hole - may be worth having a read of the introductions to articles on stellar evolution, black holes and degeneracy pressure.

Current theory (I think) is that the SMB and galaxy formed together - but that is still model dependent. Every few months you see a different version of it!

astromark
2010-Nov-29, 07:07 PM
Yes 'Shaula' you have encapsulated the whole Black Hole formation and in a very easy to understand method. The intent of your post. Great.

Can we answer this question ? Where are the nearest to us BH's... massive or moderate ? and, in what direction might they be wandering ?

Do I need 'Stary night' ?

Gamefreak89
2010-Nov-29, 07:31 PM
Yes 'Shaula' you have encapsulated the whole Black Hole formation and in a very easy to understand method. The intent of your post. Great.

Can we answer this question ? Where are the nearest to us BH's... massive or moderate ? and, in what direction might they be wandering ?

Do I need 'Stary night' ?

Are you trying to scare me and ruin my Christmas kind sir?! lol XD just kidding I don't want that kind of stuff to wonder around in my mind because it usually will get stuck there for a while making me have sleepless nights lol. But anyways I don't think there is no known BH's heading this way if there were then Newton or gallileo would've probably seen it or even astronomers back in the early 20th century would've seen it.

astromark
2010-Nov-29, 08:08 PM
*Craps his pants* Are trying to scare me and ruin my Christmas kind sir?! lol XD just kidding I don't want that kind of stuff to wonder around in my mind because it usually will get stuck there for a while making me have sleepless nights lol. But anyways I don't think there is no known BH's heading this way if there were then Newton or gallileo would've probably seen it or even astronomers back in the early 20th century would've seen it.

:eek: and a little, :razz::rolleyes:Lol...NO, no, no...I know of NO danger from this for humanity.. Nor do I suggest one...
I just wish to know where one might look to see one of these things... Knowing that Sagaterious A is not viewable from my point of view.
Its a interesting subject. That has had a fare share of description...Have I missed the answer to the OP ? just interested... nothing more.

antoniseb
2010-Nov-29, 08:19 PM
... I don't think there is no known BH's heading this way if there were then Newton or gallileo would've probably seen it or even astronomers back in the early 20th century would've seen it.

Wandering black holes are a very low likelihood of being our demise. Still, going back to the OP, I calculated that the nearest one was probably about 50-100 light years away. If the black hole is from a star in THIS galaxy, it might be moving about 5 miles/second compared to the Sun. If it is from the Arcturus stream (remnants of a galaxy merging with us), it might be going MUCH faster. You might only get a few centuries notice before the orbits of the planets get slightly disrupted.

Gamefreak89
2010-Nov-29, 08:28 PM
Staying on topic antoniseb what did you mean by galaxy merger? Did you mean that a dwarf galaxy is colliding with us right now? Or already has? But what I really want to know is that a dwarf galaxy does have a SMB right? If so how big would it be?

Grey
2010-Nov-29, 08:50 PM
But I'm serious on one thing though it used to frighten me to death back in my early to mid teenage years and I'm only 20 years old lol but staying on topic antoniseb what did you mean by galaxy merger? Did you mean that a dwarf galaxy is colliding with us right now? Or already has?It appears that our galaxy is in the process of absorbing a fair number of dwarf ellipticals and globular clusters; this appears to be relatively common for large galaxies. Take a look here (http://en.wikipedia.org/wiki/List_of_stellar_streams) for some details.


But what I really want to know is that a dwarf galaxy does have a SMB right? If so how big would it be?Dwarf galaxies don't appear to have supermassive black holes. Some of them might have intermediate mass black holes, but we don't really have enough information to know whether that's typical for a dwarf galaxy or not.

Shaula
2010-Nov-29, 10:52 PM
Can we answer this question ? Where are the nearest to us BH's... massive or moderate ? and, in what direction might they be wandering ?
Nearest ones are stellar remains black holes - as far as we know. They are a few solar masses, nothing like the monster at the heart of the galaxy. The ones we know of are generally either part of a supernova remnant or in a binary system. Some candidates are:
Cygnus_X-1 (http://en.wikipedia.org/wiki/Cygnus_X-1) - 6000ly away
Cygnus_X-3 (http://en.wikipedia.org/wiki/Cygnus_X-3) - very bright object 37000ly away
A0620-00 (http://en.wikipedia.org/wiki/A0620-00) - about 3500ly away, quite a nearby one

Wikipedia has a long list of candidates. There is a range of masses with the top one being 15 Ms or so, the smallest 4 Ms or so.

As for wandering - most don't really wander than fast. The only ones I have read about that move are ones ejected from a supernova (which is quite rare) and ones thrown out of globular clusters. We don't know of any on their way here though.

Gamefreak89
2010-Nov-30, 06:05 AM
That is a good thing then that means I can sleep at night :D but it is interesting on how there are different types of Black Holes I wonder how many different sizes there are for one?

Shaula
2010-Nov-30, 07:03 AM
Black hole masses can theoretically be a continuum. But they tend to come in size brackets depending on how they formed/where they are. So you get ones that are or the order of solar masses (say 1-50) which are from supernovae, you get ones that are enormous (thousands of solar masses) that are at the centre of galaxies. There are speculations that you get some intermediate mass ones (hundreds of solar masses) and micro ones (thousandths of solar masses and smaller) but little evidence. In general you can consider them to be burnt out stars or galactic cores - there are exceptions and possibly exotics like micro black holes and intermediate ones but we haven't seen them for sure yet.

astromark
2010-Nov-30, 07:21 AM
The voice of reason... Yes. Thanks Shaula... you nailed it.

Strange
2010-Nov-30, 10:57 AM
There is some evidence that there are fewer black holes than expected in the 2 to 5 solar mass range: http://arxiv.org/abs/1006.2834 (although it seems to be based on a limited number of samples).

Gamefreak89
2010-Nov-30, 01:35 PM
I've also heard that BH's can be seen with different types of lensing I think but my mind is limited on this sort of subject because I hardly no nothing about what BH's really look like under the scope of a telescope or by a satellite.

Shaula
2010-Nov-30, 05:40 PM
We have never directly seen one through a telescope or from a satellite. The ones we know about are surrounded by an accretion disk and it is the radiation from this that we see. Black holes bend light and so from up close you'd see some really strange effects due to this gravitational lensing. From further away it'd be harder to tell if the lensing object was a black hole or not unless you got very good temporal resolution.

loglo
2010-Dec-01, 01:59 PM
The front cover of Taylor/Wheeler (http://www.amazon.com/Exploring-Black-Holes-Introduction-Relativity/dp/020138423X) has a depiction of Saturn if a black hole was disturbing the view. The distorted ring section in the centre of the picture is behind Saturn in the undistorted view. The increase in the image size is also part of the effect.

Gamefreak89
2010-Dec-02, 10:49 AM
Interesting also I believe Phil Plait has a book on this as well so anyways how big around would the accretion disk be? Or how large would the BH itself be?

Shaula
2010-Dec-02, 11:48 AM
Size of a black hole depends on its mass. 10 solar masses ~ 25km in radius. They are the normal star ember ones. Supermassive black holes can be a few AU (distance from the Sun to the Earth) across. But the larger they are the less dramatic the gravitational effects are near the event horizon. Most of the effects we think of (stuff being ripped apart) are due to tidal fores which are greater for smaller objects.

Accretion disks can be just about any size depending on the amount of matter locally and the central object. You are normally looking at up to solar system size (generally smaller IIRC) for stellar black holes.

eburacum45
2010-Dec-05, 06:11 PM
I think it is entirely possible that a solitary, stellar-mass black hole would have no significant accretion disk. In fact solitary, disk-less black holes might be in the majority. Some, or many, or most supernova candidates will have no close companion.