Blackhole at the center of each galaxy, think again

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SUMMARY

The discussion centers on the existence of massive black holes at the centers of galaxies, particularly focusing on the Milky Way's black hole, Sagittarius A* (Sgr A*). Participants assert that rapid stellar motion near Sgr A* provides strong evidence for its existence, despite challenges in observing similar phenomena in other galaxies due to dust and distance. They emphasize that while black holes are small, their gravitational effects can lead to observable phenomena, such as gravitational lensing. The conversation highlights the need for advanced technology to study distant galaxies effectively.

PREREQUISITES
  • Understanding of black hole physics, specifically Sagittarius A* (Sgr A*)
  • Knowledge of gravitational lensing and its implications
  • Familiarity with infrared astronomy and its role in observing celestial bodies
  • Awareness of stellar motion dynamics in galactic centers
NEXT STEPS
  • Research the effects of gravitational lensing on light from stars near black holes
  • Study the techniques used in infrared astronomy for observing galactic cores
  • Explore the dynamics of stellar motion around Sagittarius A* and its implications for black hole existence
  • Investigate the technological advancements needed for observing distant galaxies
USEFUL FOR

Astronomers, astrophysicists, and students interested in black hole research and the dynamics of galaxies will benefit from this discussion.

  • #31
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

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
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
 
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  • #34
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
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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