black-holes do not exist

[north]

it has been suggested that black-holes exist in all galaxies

 

I disagree

 

if black-holes do exist in the center of galaxies then why is light eminating from these galaxies ?

[Realitycheck]

The overall density of the immense number of stars in them.

[big314mp]

Light that is beyond the event horizon (i.e. the edge) of a black hole is not sucked in.

[north]

The overall density of the immense number of stars in them.

 

suggesting that ....?

 

Light that is beyond the event horizon (i.e. the edge) of a black hole is not sucked in.

 

but there is no evidence that any light is being sucked in by any galaxy

[iNow]

it has been suggested that black-holes exist in all galaxies

 

I disagree

Good for you. You're welcome to your own opinions, but not your own facts.

 

 

 

http://chandra.harvard.edu/xray_sources/blackholes.html

 

Supermassive black holes with the mass of many millions of stars are thought to lie at the center of most large galaxies. The evidence comes from optical and radio observations which show a sharp rise in the velocities of stars or gas clouds orbiting the centers of galaxies. High orbital velocities mean that something massive is creating a powerful gravitational field which is accelerating the stars. X-ray observations indicate that a large amount of energy is produced in the centers of many galaxies, presumably by the in-fall of matter into a black hole.

 

How could a supermassive black hole form in the center of a galaxy? One idea is that an individual starlike black hole forms and swallows up enormous amounts of matter over the course of millions of years to produce a supermassive black hole. Another possibility is that a cluster of starlike black holes forms and eventually merges into a single, supermassive black hole. Or, a single large gas cloud could collapse to form a supermassive black hole.

 

 

Centaurus ARecent research, including results from Chandra (see 3C294, Perseus Cluster, NGC 4636, Centaurus A) suggests that galaxies and their black holes do not grow steadily, but in fits and starts. In the beginning of a growth cycle, the galaxy and its central black hole are accumulating matter. The energy generated by the jets that accompany the growth of the supermassive black hole eventually brings the infall of matter and the growth of the galaxy to a halt. The activity around the central black hole then ceases because of the lack of a steady supply of matter, and the jets disappear. Millions of years later the hot gas around the galaxy cools and resumes falling into the galaxy, initiating a new season of growth.

[north]

further there should be two event horizions at complete opposite ends of each other , there is no evidence of this

[big314mp]

but there is no evidence that any light is being sucked in by any galaxy

 

What exactly would you use to prove that light got sucked in by a black hole? It's not exactly something that can be directly observed.

 

There is plenty of info out there about black holes, as iNow has posted.

[iNow]

further there should be two event horizions at complete opposite ends of each other , there is no evidence of this

 

I agree. There is no evidence that there should be two event horizons at complete opposite ends of each other.

[big314mp]

Opposite ends of what? A black hole is a sphere...

[north]

Good for you. You're welcome to your own opinions, but not your own facts.

 

 

 

http://chandra.harvard.edu/xray_sources/blackholes.html

 

Supermassive black holes with the mass of many millions of stars are thought to lie at the center of most large galaxies. The evidence comes from optical and radio observations which show a sharp rise in the velocities of stars or gas clouds orbiting the centers of galaxies.

 

perhaps but the light from the galaxies eminates from any angle

 

 

 

 

 

 

High orbital velocities mean that something massive is creating a powerful gravitational field which is accelerating the stars. X-ray observations indicate that a large amount of energy is produced in the centers of many galaxies, presumably by the in-fall of matter into a black hole.

 

presumably is the key

 

and so far a black-hole explaination is assumed rather than proven

 

How could a supermassive black hole form in the center of a galaxy? One idea is that an individual starlike black hole forms and swallows up enormous amounts of matter over the course of millions of years to produce a supermassive black hole. Another possibility is that a cluster of starlike black holes forms and eventually merges into a single, supermassive black hole. Or, a single large gas cloud could collapse to form a supermassive black hole.

 

when looked at three dimensionaly , there should be evidence of two points at which the black-hole does this

 

there is not

 

 

 

 

Centaurus ARecent research, including results from Chandra (see 3C294, Perseus Cluster, NGC 4636, Centaurus A) suggests that galaxies and their black holes do not grow steadily, but in fits and starts. In the beginning of a growth cycle, the galaxy and its central black hole are accumulating matter. The energy generated by the jets that accompany the growth of the supermassive black hole eventually brings the infall of matter and the growth of the galaxy to a halt. The activity around the central black hole then ceases because of the lack of a steady supply of matter, and the jets disappear. Millions of years later the hot gas around the galaxy cools and resumes falling into the galaxy, initiating a new season of growth.

 

so the jets suggest a two point event horizion

 

true ?

[Realitycheck]

suggesting that ....?

 

Just because there is a supermassive black hole at the center (not all of them have one) does not mean that the light from 500 billion stars could just somewhat hide the black hole. Right?

[north]

[Originally Posted by north

suggesting that ....?

 

Just because there is a supermassive black hole at the center (not all of them have one) does not mean that the light from 500 billion stars could just somewhat hide the black hole. Right?

 

your right

 

there would have to be some evidence that the light from at least those stars that are the closest to the globular center of the galaxy , have their light affected by any black-hole present

 

but so far none exists

 

but not only that , the light coming from the galactic globular center shows no signs of being affected either , by any black-hole physical dynamic consequences ,

 

at all really

[big314mp]

there would have to be some evidence that the light from at least those stars that are the closest to the globular center of the galaxy , have their light affected by any black-hole present

 

but so far none exists

 

but not only that , the light coming from the galactic globular center shows no signs of being affected either , by any black-hole physical dynamic consequences ,

 

at all really

 

Gravitational lensing?

 

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

[CaptainPanic]

I'm a little puzzled over the definition of "fact" when we are discussing astronomical phenomena. "Fact" is not the same as "most accepted explanation". About 400 years ago, it was widely accepted that the earth is flat. However, I would not go as far as saying that it was a fact that 400 years ago the earth was flat. This statement was triggered by:

Good for you. You're welcome to your own opinions, but not your own facts.

 

And then you quote some text, which starts with a sentence which clearly does not give a fact, but merely a suggestion.

 

http://chandra.harvard.edu/xray_sources/blackholes.html

Supermassive black holes with the mass of many millions of stars are thought to lie at the center of most large galaxies.

 

I am not certian what we should do with this "fact". I suggest that when you tell others to show facts, that at least you do so yourself.

 

(same article that iNow quoted) High orbital velocities mean that something massive is creating a powerful gravitational field which is accelerating the stars. X-ray observations indicate that a large amount of energy is produced in the centers of many galaxies, presumably by the in-fall of matter into a black hole.

That I don't understand. If I fill my bathtub, and then empty it. The water will spin at the drain. There is a large acceleration near the center, but I have seen no evidence of a black hole near that particular rotating system. (This is no proof though, since you cannot see black holes).

 

The stars that are present in a galaxy all add to the massive gravitational field... the center of mass of the whole galaxy lies in its center (duh), so logically, that is what all stars rotate around. But it is not necessary for any rotation to have a heavy mass in the middle... as long as the center of mass is in the middle (which it always is, by definition).

 

X-ray observations indicate that a large amount of energy is produced in the centers of many galaxies, presumably by the in-fall of matter into a black hole.

This point I have no idea about... is there any proof (not models that just appear to cover some observations) that a black hole creates X-ray radiation?

 

Anyway, all sentences in this article have words that clearly indicate that we're not so sure how things work: "suggest", "probably", "presumably" etc.

[D H]

Let's go back to the start. North, you seem to have a misconception of what a black hole is and in particular, what an event horizon is. From these misconceptions you have leapt to some erroneous conclusions.

 

A black hole is a concentration of mass in a very small volume, so small that at sufficient proximity the escape velocity exceeds the speed of light. This surface inside which even light cannot escape the black hole is the event horizon. For a non-spinning black hole the event horizon is a sphere, and very small sphere at that.

 

This is your first misconception. A black hole is small. The event horizon for a stellar black hole with a mass of five solar masses is a mere 30 kilometers across. Even a supermassive black hole is tiny. The black hole hypothesized to exist at the center of the Milky Way, with a mass of 4 million solar masses, is 25 million kilometers in diameter. That might sound big, but it's not. That black hole would fit inside the orbit of Mercury.

 

Forget about the gravitational issue for a bit. Suppose there exists some exotic object that has absorbs all light that hits it but has very little mass. Now imagine one of these objects 25 million kilometers across at the center of some galaxy. Could we see any signs of this object if we aimed a telescope on that galaxy? No. It's too small. Seeing that object would be akin to seeing a grain of dust flying in front of the sun. Even worse, it would be akin to seeing a grain of dust flying behind the sun.

 

Your second misconception is that stuff about jets and a "two point event horizon". The event horizon for a non-spinning black hole is a sphere, not a pair of isolated points. Things get a lot trickier for spinning black hole, but the event horizon is still an oblate spheroid. Infalling matter toward a spinning black hole will form an accretion disk, somewhat similar to the way a star system forms. (Look at our solar system; the planets all orbit in roughly the same plane.) The jets you are talking about do not come from the black hole itself (nothing escapes a black hole); they come from the accretion disk and are directed along the accretion disk axis.

 

Since we can't see black holes, even supermassive ones, how do we detect them? One way to detect black holes is by means of the radiation given off by the accretion disks, particularly the jets. Another way is to look at stars at the center of a galaxy.

 

Suppose astronomers detect a star closely orbiting something at the center of some galaxy. They can infer the mass of that thing the star is orbiting from the nature of the star's orbit. We know there is some very small object at the center of our galaxy with a mass of 4 million suns. A supermassive black hole is one possibility. Any other candidates made of stuff we know (e.g., a bunch of neutron stars) could not exist in that proximity and fail to form a black hole. So that thing in the center of our galaxy is a supermassive black hole, or something like nothing else we know of in the universe.

[Zolar V]

Bravo, that was a wonderful concise explanation.

You basically took several chapters in a physics textbook and extracted all of the relevant information for this post.

[Mr Skeptic]

A very good explanation by D H there. Let me add one more thing.

 

What we see here (in the start of this thread) is another victory of the "Vacuum Cleaner Model" of black holes, in which black holes suck up everything nearby in violation of the laws of physics as they exist outside of scifi movies. Although in scifi movies if something collapses into a black hole it starts sucking everything nearby in, in real life you would not notice the difference. The gravitational attraction would not be increased, and the law of conservation of momentum and energy would not be suspended. If you were orbiting about the object before it collapsed into a black hole, you would remain in the same orbit. If there were any change, it would be very small.