Evidence for Black Hole in Galactic Center

[astroron (Ron)]

Latest on Massive Black Hole in the Galactic Center
http://news.bbc.co.uk/2/hi/science/nature/7774287.stm
Ron

[sheeny (Al)]

Got a link, Ron?

Al.

[astroron (Ron)]

OOOPS Sorry Al
Ron

[xelasnave]

Thanks Ron I like the artist impression but I still wonder about their determination to infer their existence and if there are not other explainations to the observational evidence they seize upon.

I note there is no metion of a companion...as I also read (not something that I wrotre either) that black holes always existed in a binarey system...maybe this one is an exception.
Thanks again I love this stuff.
alex

[sheeny (Al)]

Originally Posted by astroron

OOOPS Sorry Al
Ron

I thought that was the evidence... the black hole got it!

Al.

[jungle11 (Greg)]

I was thinking perhaps many supposed black holes have been found because there was a nearby star to give them away by their effects on that star/ Perhaps that might explain the binary theory?

From that article, it sounds like the really massive ones at the centre of galaxies might have been created in the Big Bang instead of collapsing stars. Which explains how the first stars were born pretty well, and the structure of galaxies too.

What are the other theories apart from black holes to explain the empirical evidence?

[Quark (Trevor)]

Originally Posted by astroron

Latest on Massive Black Hole in the Galactic Center
http://news.bbc.co.uk/2/hi/science/nature/7774287.stm
Ron

Hi Ron,
Andrea Ghez of the UCLA Keck Galactic Centre Group is probably the Worlds leading authority on this. She has been studying the high velocity stars in orbit around the super massive black hole candidate Sag A*(pronounced Sag A star) for over 15 yrs. The star in closest orbit S02, which attains a velocity of 6000 km/sec at closest approach, it has a very elliptical orbit.

In August this year Andrea Ghez reported on her data for a complete orbit of S02. This enabled her to refine not only the mass of Sag A* but also the distance to the Galactic Centre (R0).

I posted her paper on this forum in a post titled "Implications of refining R0"

When I work out how to post a link to it I will include it in another reply.

Regards
Trevor

[Quark (Trevor)]

Hi again Ron,
This is the link to the post I referred to on the super-massive black hole candidate at our galactic centre, Sag A*


http://www.iceinspace.com.au/forum/s...ad.php?t=35557


The links to her website are also worth a look, particularly the animation of 15 yrs worth of data of the high velocity stars in orbit around Sag A*.

Regards
Trevor

[DJDD]

I just had a look at the animation of star movements- very cool.
And

Sure, S0-2's orbit was complete but look at S0-16; its 'orbit' looks wild!

and what a difference adaptive optics makes.

[astroron (Ron)]

Sorry Trevor, I missed your original post.
I have seen data on other places, but this article was saying that this is the definitive proof.
As with the stuff speeding round black holes it is hard to keep up with this subject.
Regards
Ron

[astroron (Ron)]

Trevor, I missed your post as I was not near a computer for about three months earlier this year
Ron

[Quark (Trevor)]

Originally Posted by astroron

Trevor, I missed your post as I was not near a computer for about three months earlier this year
Ron

No worries Ron,

There is a lot of info out there on this subject, much of it is somewhat dated, a reflection of the pace at which research is progressing.

We really do live in a golden age of discovery, it is unfortunate that much of it doesn't filter down to the general population.

I became interested in the work of Andrea Ghez back in 2004 when I was doing my degree at Swinburne. I was writing an essay on "The Distance to the Galactic Centre" for Professor Duncan Forbes.

Her work fascinated me, particularly regarding how refinement of Ro (the distance to out galactic centre), by a direct measurement method, would result in a refinement of the absolute luminosity of the variable stars in the Sag A* region. This would then lead to a refinement of the distance ladder.

If you are interested in keeping abreast of the latest research, really in just about any field of astronomy then I would highly recommend the NASA ADS Abstract data base.

Regards
Trevor

[bojan]

Originally Posted by xelasnave

Thanks Ron I like the artist impression but I still wonder about their determination to infer their existence and if there are not other explainations to the observational evidence they seize upon.

Alex,
If you read the paper (link provided by Trevor), in abstract it says:

"ABSTRACT
We report new precision measurements of the properties of our Galaxy’s supermassive black hole.
Based on astrometric (1995-2007) and radial velocity (2000-2007) measurements from the W. M. Keck
10-meter telescopes, a fully unconstrained Keplerian orbit for the short period star S0-2 provides values
for the distance (R0) of 8.0 ±0.6 kpc, the enclosed mass (Mbh) of 4.1 ±0.6 ×10 6 M ⊙, and the black
hole’s radial velocity, which is consistent with zero with 30 km/s uncertainty. "

Now, instead of black hole, you can substitute word "object"

What that object could be, in your opinion, considering mass of 4.1 millions Solar masses, in such a small volume of space ?

Originally Posted by xelasnave

I note there is no metion of a companion...as I also read (not something that I wrotre either) that black holes always existed in a binarey system...maybe this one is an exception.

Black holes of stellar masses (not supermassive, like in centres of galaxies) are sometimes part of binary systems. The paper in question does not deal with those "small" objects.

[xelasnave]

Thanks for all that Bojan.

Without rattling on I suspect that instead of a single object of massive gravity we will find still massive objects but in binary systems and it is the binary system that produces the extreme gravity..and the massive jets for that matter. (and this science is far to complex to be explained with maths by the way) but that was to answer your question and I except your frustration and should not have let it in the door.

Having said that and being entirely sensible for a moment I follow and respect all conventional work and read every news release that turns up in the science sites I follow. Anything black or dark I have read about it.

My objection with black holes is in the name because I got sick a long time ago explaining to folk it was not like a drain hole in the sink... and the disappointment that a realistic relevation dealt them.

Not as appealing if you say think of a ball or think of it like a star..but very dense..denser than me my friend..they then get it... In fact I object to the disposal of many matters to the black basket..black or dark.

I would prefer a "Densersiod" or "Superdensersoild" or simply Massive stellar object...but black hole...so unfortunate a throw away line used in ridicule has stuck... as did "big bang" .... I think they need a name that gives respect to the profession of astronomy and does not encourage stupid movies.

alex

[xelasnave]

Also now that we have a mass we can work out how far the force of gravity will reach from our black hole and work out being as massive as they have found it to be just how much it influences the rest of the galaxy..... by the inverse square rule no doubt... so how far does its "power" reach out???

Will we feel any attraction here? where will the attraction die off I wonder?

alex

[Zuts]

Originally Posted by xelasnave

Also now that we have a mass we can work out how far the force of gravity will reach from our black hole and work out being as massive as they have found it to be just how much it influences the rest of the galaxy..... by the inverse square rule no doubt... so how far does its "power" reach out???

Will we feel any attraction here? where will the attraction die off I wonder?

alex

Gravity travels at the speed of light, since the object is only 27,000 light years away and since it has been there far longer than us, we have always felt its attraction...at a tried and true 1/r2 dropoff.

Remember, gravity is a very weak force. A simple fridge magnet can lift a paperclip from the surface of the earth, so the magnetic force of this tiny thing is stronger than the gravitational field of the entire earth!

The 1/r2 dropoff means the force at the surface of the earth compared to the force at the event horizon is gazillions of times weaker.

Cheers
Paul

[xelasnave]

Thanks Paul it is the drop off that I point to.
As massive as it is I doubt its influence really goes as far as most may assume. I read something and cant remember a thing but it pays to actually get its actual influence in perspective..it surprised me. and there is other stuff how they clean out only a certain region from recollection...brain is going down hill I am afraid I have had to drop so much data to fit more in...
alex

[leinad (Dan)]

Thanks for the update. Amazing!

[timb (Tim)]

Originally Posted by xelasnave

Thanks Ron I like the artist impression but I still wonder about their determination to infer their existence and if there are not other explainations to the observational evidence they seize upon.

I note there is no metion of a companion...as I also read (not something that I wrotre either) that black holes always existed in a binarey system...maybe this one is an exception.

They have identified 28 stars orbiting the black hole, so it is minimally part of a 29-ary system.

[xelasnave]

Originally Posted by timb

They have identified 28 stars orbiting the black hole, so it is minimally part of a 29-ary system.

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.


alex