Do we know whats at the center of galaxies yet?

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    Center Galaxies
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Discussion Overview

The discussion centers around the nature of the center of galaxies, particularly the Milky Way, and whether it is accurately described as a supermassive black hole (SMBH). Participants explore the characteristics of the galactic core, its brightness, and the evidence supporting the black hole hypothesis, while questioning the completeness of current theories.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions the classification of the galactic core as a black hole, noting its brightness and lack of apparent characteristics typical of black holes.
  • Another participant asserts that the evidence strongly supports the existence of a SMBH, citing constraints on its mass and size based on the orbits of nearby stars.
  • A third participant suggests that there may be confusion regarding the term "core," indicating that while there is a cluster of stars, there is also a dark object at the center whose presence is inferred from stellar orbits.
  • Links to external resources are provided for further reading on the topic, including animations and articles that illustrate the orbits of stars around the central object.

Areas of Agreement / Disagreement

Participants express differing views on the characteristics of the galactic core and the validity of the black hole model. There is no consensus reached regarding the completeness of current theories or the nature of the central object.

Contextual Notes

Participants highlight the limitations of current understanding, including the ambiguity in defining the "core" of the galaxy and the reliance on indirect observations of stellar orbits to infer the presence of a central object.

Topher925
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Probably a stupid question as I'm sure we don't but stargazing gets me thinking. The last prevailing theory that I heard of was a massive black hole at the center of the milky way (and all other galaxies). However, the core of the galaxy is the brightest part by far and other than extremely large amounts of gravity, it doesn't appear to have any other characteristics of a black hole (as far as I know anyway). Are there any other creditable theories out there?
 
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Topher925 said:
...it doesn't appear to have any other characteristics of a black hole...
Such as?

We're pretty sure it's a SMBH. It has a lower constraint on its mass, based on objects in orbit around it. It also has an upper constraint on its size - also based on objects in orbit around it. The only object we know of with that mass and that radius is a black hole.

Here's a cool animation showing the orbits of some of the stars in VERY close orbit.
http://chargedmagazine.org/2012/05/supermassive-black-hole-causing-a-stir-in-the-milky-way/
SO-16 virtually grazes it, defining at least one upper limit on its size.

Based on orbits like these, calculations show the object can't be larger than our solar system, in fact, not larger than Jupiter's orbit I think.

There's a thread here on PF somewhere that goes into more detail.
As for brightness, our SMBH is closely surrounded by a very dense group of many, many millions of stars. That's why the core as a whole is so bright.
 
Last edited:
Topher925 said:
However, the core of the galaxy is the brightest part by far and other than extremely large amounts of gravity, it doesn't appear to have any other characteristics of a black hole (as far as I know anyway). Are there any other creditable theories out there?

Read this article: http://en.wikipedia.org/wiki/Supermassive_black_hole
 
Topher925 said:
However, the core of the galaxy is the brightest part by far and other than extremely large amounts of gravity, it doesn't appear to have any other characteristics of a black hole (as far as I know anyway).

I think there is confusion about what is mean by "core". There is indeed a cluster of stars about 1000 light years across, but at the center of that, there is this mysterious dark object and we can tell what it's doing by seeing the nearby stars orbits around it.
 

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