Evidence for Black Hole in Galactic Center

[jungle11 (Greg)]

I dont think the black whole could be moved by 27 companions? I guess it must be, but the amount would be to negligable to be measured?

I thought perhaps the black hole's gravity well, would be strong enough to attract a layer of stars around it, and then the gravity of those stars would continue to repeat the process, creating the galactic bulge in the centre. Then, further out from the centre the rotation of the galaxy would flatten out the disk? I have no idea - just wondering.

I read something a while ago about galaxies having measurable magnetic fields? Does that explain the structure?

Could our solar system be held in orbit around the core by the combined mass of the billions of stars towards its centre...

[bojan]

Greg,
those 29 stars are just objects in the immediate vicinity of that monster (remember, 4 million solar masses!) and it was possible to (relatively) easily detect and monitor their movement around it. By all means there are more around, invisible to us (at present) which are also orbiting BH.

The mass of BH is so much larger that it stays rock solid in the centre of gravity of that small system (29 stars) ..
However, the whole that bunch orbits the gravitational centre of the galaxy.. Newton's laws are valid here as well. Most likely, the centre of gravity of the whole galaxy is not far away, though.

[timb (Tim)]

Originally Posted by xelasnave

Yes apparently there are a few but there is a difficulty is descibing such a system... its not a 29 ary if they orbit the black hole,,,more like a planetary system in that context... mmm

AND is the black hole at the very center of the galaxy (and how we work out the exact centre would seem difficult) or does it orbit the "centre" in counter balance to its "companions"

I was inclined to think black holes held the rest of the galaxy in place (an incorrect assumption) but it seems they play little part because their gravitational influence does not extend very far at all.

So it is interesting to wonder what their part is in the scheme of things...they do not seem to be anchor points as it were... they are not to the galaxy what our sun is to our solar system in so far we orbit the Sun because of its gravity influence...the solar system does not orbit in the galaxy because there is a black hole at its center... so that is curious.

True, the orbiting stars are less to that black hole than the Earth is to the Sun. I was being pedantic. That is one of my special abilities. If you define the MBH as a star, and you seem happy to do so if the BH is of stellar mass, then our friend Sgr A* and the many stars that dance attendance upon it are a multiple star system. There are quite a few papers on arXiv about SMBHs. They generally star close to the galaxy's centre of mass.

[xelasnave]

Thanks for the link Timb.
I highly respect the quality of being pedantic.
For a black hole to exert a gravitational influence even before we apply the inverse square rule it would need a mass to balance the other stars in the galaxy which on current estimate is some 350 billion stars...if we then apply the inverse square rule the black hole would have to be trillions of solar masses...maybe more.
AND so at the risk also of being pedantic I say that this simple observation must remove some of the importance many seek to apply to a black hole.. the significance their gravitational influence I feel is greatly overestimated (in fact not estimated so simple questions such as I raise may be considered) and therefore their role in any influence upon galaxy evolution seems to me be grabbed at without a realisation no matter how massive we believe them to be their mass seems hopelessly inadequate to support current beliefs that they somehow control the galaxy overall...I dont know this is the view of those at the coal face but that is an impression I feel is popular...but it may just be my misinterpretation of various articles that have come before me.

I believe that as a generalisation black holes tend to clean out a region and when this happens they then tend to do little more... they have cleaned out what they can effect gravitationally and their power can not draw in more stars because their gravity can only reach so far to pull in new matter.

Never worry about being pedantic it is better than many other qualities humans put above it.

alex

[bojan]

Alex, do not jump into the pot, without checking what's cooking in it...
You are making conclusions and judgements without any previous analysis (oh.. I wonder what's new about it ) to support such claims.
We have been here before: Science is not a belief system, it is self-sustained system where things get checked and re-checked again and again.. not with words, but with mathematical analysis supported with observations and vice versa.

Have you played with gravitational simulator at all, ever?
Of course, PC is not powerful enough to show how the whole galaxy behaves (with it's BH in the middle) but some time spent with one of them and playing with couple of masses and their interactions may give you an insight into complexity of so simple at a first glance function: 1/r^2.

[astroron (Ron)]

APOD for today 11/12/08
http://antwrp.gsfc.nasa.gov/apod/astropix.html
Ron

[xelasnave]

Bojan said........

You are making conclusions and judgements without any previous analysis

I can understand I may seem casual in comment but I dont think anything I have said has been said without thinking long and hard about the stuff I read (leaving aside the alternative idea re black holes which I have left at the door)...and I would say the maths may just support the proposition I ponder upon...

I make a simple observation which is ...a black hole as powerful as we can conceive still will not approach the gravitational power to influence very much of the galaxy ...thanks to the inverse square rule gravitational influence diminishes such that if one were to rely on a black hole having gravitational influence over the whole galaxy it would have to be trillions of solar masses.... and When I get a recharge on this 3g I will look at the stuff I read about black holes clearing out inner regions that came from research not my imagination is my point...and that stuff came from science sites so I am not claiming this is my original thought ...

As to a gravitational simulator yes but what can they tell you if they overlook the simple math I suggest needs to be considered...if a simulator can simulate other than I suggest check it with the simple math... but such is not relevant all that is relevant is a black hole has little gravitational influence on the galaxy... it has or it has not...If we say Sag A is a billion solar masses how far can it influence???.

I dont know really but the way I work out things I am of the current opinion which can be destroyed with simple math or the simple math will support my general proposition...either way I am right or wrong I dont care but my views are not engineered without considerable thought...and I form a belief...there are few facts that can not be termed beliefs irrespective of how convinced folk are of their truth....in my humble opinion...


And thanks Ron for the link but After this psot I will be out of fun tickets for the net so I wont get to look at it till much later.


alex

[xelasnave]

Here is some research on the upper limit of black holes and an a suggestion as to why which indicates why I formed the impression that their role is less than that of apparent popular belief.

http://www.sciencedaily.com/releases...0909095133.htm

however we have the prospect of lots of them also

http://www.sciencedaily.com/releases...0111090506.htm

alex

[xelasnave]

Black holes are doughnut shaped according to this......
http://www.sciencedaily.com/releases...1216104311.htm

well the matter outside follows this shape it seems
alex

[xelasnave]

Rapid spin.....
http://www.sciencedaily.com/releases...0110150936.htm
alex

[xelasnave]

Binary black holes
http://www.sciencedaily.com/releases...1120072341.htm
alex

[xelasnave]

http://www.sciencedaily.com/releases...0222195058.htm

This points to the clean out thing I raised...and suggests an upper mass limit...

alex

[glenc (Glen)]

http://news.bbc.co.uk/2/hi/science/nature/7815827.stm
A cosmic chicken-and-egg question has been solved by astronomers, who now say that black holes came before galaxies.
The findings were presented at a major astronomy meeting in California.
Most if not all galaxies, including our own Milky Way, are believed to have massive black holes at their cores...

[Paddy (Patrick)]

Yesterday's Astronomy Picture of the Day was a nice infra red composite view of the galactic core, including the cluster around Sag A*. Well worth a look!

http://antwrp.gsfc.nasa.gov/apod/ap090107.html