Blackhole at the center of each galaxy, think again

  • Thread starter Anomalous
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  • #26
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What ST is saying is that , for a star to be visible behind the galactic centre, the star has to be exceptionally bright since light coming from ordinary stars would be lost behind the BH due to less intensity of its light as compared to exceptionally strong GRfield of a BH
 
  • #27
Anomalous
Dr.Brain said:
What ST is saying is that , for a star to be visible behind the galactic centre, the star has to be exceptionally bright since light coming from ordinary stars would be lost behind the BH due to less intensity of its light as compared to exceptionally strong GRfield of a BH
So U mean to say that the stars that are orbiting the BH are not gona show unusual orbits or are their orbits exactly perpendicular to us ?
 
  • #28
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Ofcourse,the stars orbiting outside the 'event-horizon' of a BH would orbit normally treating the BH as a lump of huge mass , but the stars 'orbiting' very near to the 'event-horizon' would move at exceptional speeds because they are literally being tried to be sucked in . Refer to ST for more information regarding what he said, he might be able to tell you more.
 
  • #29
turbo
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Anomalous said:
At least even if stars are not behind the BH yet we should be able to observe unusual deviations in the orbit of near by stars that are practivcally impossible; but visible due to light bending.
Please visit this page and wait for the animation to load. The animation is a composite of 6 years of observation of the black hole in the core of the MW. The orbits of stars affected by the BH are clearly shown.

http://www.einstein-online.info/en/spotlights/milkyway_bh/
 
  • #30
SpaceTiger
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Anomalous said:
So now from the link by Turbo we know that the BH is 20light minutes wide
This is an observational upper limit, meaning the black hole must be smaller than that (we can't actually see it). In actuality, it's probably more like 25 light-seconds wide.


So what is the size of its Event Horizon and is it related with the space bending thing and the light bending. And hence should we not see the nearby stars at wrong places.
If the black hole is close to its theoretically predicted size (~0.05 AU) and the nearest star is around 45 AU, then gravitational lensing effects would be negligible.
 
  • #31
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Chandra Observations

I'm surprised these haven't been mentioned in this context:

http://http://www.sciencedaily.com/print.php?url=/releases/2005/01/050111090506.htm [Broken]

I think stuff is awesome because it demonstrates well both the curvature of space and the illusion of dimension from outside the core. That is, while we might measure the diameter in light years from our perspective using angular measurement the actual dimensions from the perspective within the core may very well be much larger.

Clearly our understanding of "Black Holes" is still in its infancy.
 
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  • #32
Chronos
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The evidence indicating SMBH reside in the cores of most, if not all reasonably sized galaxies, is not derived from observations of individual stars. That is well beyond our technology. It is hard enough to resolve individual stars in the core of our own galaxy. Some armchair material to consider:

http://webdisk.berkeley.edu/~kshapiro/cosmo_project.htmlhttp://webdisk.berkeley.edu/~kshapiro/cosmo_project.html [Broken]
 
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  • #34
Garth
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SpaceTiger said:
This is an observational upper limit, meaning the black hole must be smaller than that (we can't actually see it). In actuality, it's probably more like 25 light-seconds wide.
The 20 light minutes probably refers to the diameter of an accretion disc around the BH.

Garth
 
  • #35
SpaceTiger
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Garth said:
The 20 light minutes probably refers to the diameter of an accretion disc around the BH.
No, we have not imaged an accretion disk around the black hole in our galaxy. They simply give numbers like this to support the idea that the object is a black hole. They can't acutally observe the event horizon itself, so they don't say that it's light-seconds across. They look at the motions of objects around it and use those place to dynamical limits on the extent of the object.
 

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