<p>Related questions have been raised before
<a href="https://astronomy.stackexchange.com/questions/16204/is-our-central-black-hole-actually-at-the-cg-of-the-galaxy">Is our central black hole actually at the CG of the galaxy?</a>
<a href="https://astronomy.stackexchange.com/questions/7861/orbiting-supermassive-black-hole-or-galactic-center-of-mass">Orbiting supermassive black hole or galactic center of mass?</a>
, where explanations have been given that the black hole should be at the center of mass. These explanations implicitly lie within the framework of widely accepted theories and models, considering only the interaction of matter within the visible three dimensions of space. However, there are hypotheses of gravitational interaction with parallel universes attempting to explain dark matter (for example <a href="https://home.web.cern.ch/science/physics/dark-matter" rel="nofollow noreferrer">[1]</a> <a href="https://home.web.cern.ch/science/physics/extra-dimensions-gravitons-and-tiny-black-holes" rel="nofollow noreferrer">[2]</a> <a href="https://astronomy.stackexchange.com/a/8088/45310">[3]</a>). In this case, the placement of the supermassive black hole nearly at the galactic center of mass is not obvious.</p>
<p>With what precision do existing measurements of star orbits in the galaxy allow us to calculate the position of the galactic center of mass? Are there measurements of the black hole's proper motion (I'm not sure relative to what, especially considering that the Sun itself moves within the galaxy), somewhat similar to measuring the proper motion of other stars?</p>
<p>The galaxy is written in the singular form, assuming that sufficiently accurate measurements could only have been made for the Milky Way. But the question is not limited to our galaxy.</p>

CC BY-SA 4.0
2024-04-24T12:28:41.147Z
We directly imaged the SagA* accretion disc a couple years ago using the Event Horizon array...  and we've measured the movements of super-speed stars like S4716 that are (as far as we can tell) directly orbiting it and swing as close as 100 AU at periapsis. Is that the sort of thing you're looking for?
Darth Pseudonym
CC BY-SA 4.0
2024-04-24T17:36:09.873Z
No, that's not it. The question concerns the center of mass of the entire galaxy and the orbits of the central supermassive black hole relative to the center.
Imyaf
CC BY-SA 4.0
2024-04-24T20:09:04.107Z
We cannot determine where the precise centre of mass of the Galaxy is. That would require detailed knowledge of the exact position and size of every mass. Why is this question not duplicating the first question you link to?
ProfRob
CC BY-SA 4.0
2024-04-25T03:08:57.880Z
There's a question is more about "why at center?". It and it's answer focuses on the evolution of the galaxy and the resulting position of the supermassive black hole in the galaxy center. Here, the question concerns measurements and their accuracy. Perhaps DR5 Gaia will be able to provide a sufficiently precise answer?
Imyaf
CC BY-SA 4.0
2024-04-25T07:44:20.320Z
It's hard to see a significant sector of the Milky Way opposite our position relative to the core. See  https://upload.wikimedia.org/wikipedia/commons/4/40/Galaxymap.com%2C_map_12000_parsecs_%282022%29.png from https://en.wikipedia.org/wiki/Milky_Way
PM 2Ring
CC BY-SA 4.0
2024-04-25T07:44:21.787Z
Thinking about the galactic center of mass is really misleading. Not only can we not measure it, there is not even a unique way to define it, since there is not a unique criterion for whether a particle belongs to the galaxy. Anyway, if you define the galaxy to include its halo, the galactic disk is not even at the center of the halo, so there's no reason to expect the central black hole to be near the overall center of mass.
Sten
<black-hole><orbit><dark-matter><galactic-dynamics><galaxy-center>
Have measurements been conducted on the position of the galactic center of mass and the orbit of the presumed black hole at the center?
Imyaf
# Have measurements been conducted on the position of the galactic center of mass and the orbit of the presumed black hole at the center?

(Asked by: username_0 on 2024-04-24)

Related questions have been raised before
[Is our central black hole actually at the CG of the galaxy?](https://astronomy.stackexchange.com/questions/16204/is-our-central-black-hole-actually-at-the-cg-of-the-galaxy)
[Orbiting supermassive black hole or galactic center of mass?](https://astronomy.stackexchange.com/questions/7861/orbiting-supermassive-black-hole-or-galactic-center-of-mass)
, where explanations have been given that the black hole should be at the center of mass. These explanations implicitly lie within the framework of widely accepted theories and models, considering only the interaction of matter within the visible three dimensions of space. However, there are hypotheses of gravitational interaction with parallel universes attempting to explain dark matter (for example [[1]](https://home.web.cern.ch/science/physics/dark-matter) [[2]](https://home.web.cern.ch/science/physics/extra-dimensions-gravitons-and-tiny-black-holes) [[3]](https://astronomy.stackexchange.com/a/8088/45310)). In this case, the placement of the supermassive black hole nearly at the galactic center of mass is not obvious.

With what precision do existing measurements of star orbits in the galaxy allow us to calculate the position of the galactic center of mass? Are there measurements of the black hole's proper motion (I'm not sure relative to what, especially considering that the Sun itself moves within the galaxy), somewhat similar to measuring the proper motion of other stars?

The galaxy is written in the singular form, assuming that sufficiently accurate measurements could only have been made for the Milky Way. But the question is not limited to our galaxy.

**Tags:** black-hole, orbit, dark-matter, galactic-dynamics, galaxy-center

> **Comments:**
> **username_1**: We directly imaged the SagA* accretion disc a couple years ago using the Event Horizon array...  and we've measured the movements of super-speed stars like S4716 that are (as far as we can tell) directly orbiting it and swing as close as 100 AU at periapsis. Is that the sort of thing you're looking for?  
> **username_0**: No, that's not it. The question concerns the center of mass of the entire galaxy and the orbits of the central supermassive black hole relative to the center.  
> **username_2**: We cannot determine where the precise centre of mass of the Galaxy is. That would require detailed knowledge of the exact position and size of every mass. Why is this question not duplicating the first question you link to?  
> **username_0**: There's a question is more about "why at center?". It and it's answer focuses on the evolution of the galaxy and the resulting position of the supermassive black hole in the galaxy center. Here, the question concerns measurements and their accuracy. Perhaps DR5 Gaia will be able to provide a sufficiently precise answer?  
> **username_3**: It's hard to see a significant sector of the Milky Way opposite our position relative to the core. See  https://upload.wikimedia.org/wikipedia/commons/4/40/Galaxymap.com%2C_map_12000_parsecs_%282022%29.png from https://en.wikipedia.org/wiki/Milky_Way  
> **username_4**: Thinking about the galactic center of mass is really misleading. Not only can we not measure it, there is not even a unique way to define it, since there is not a unique criterion for whether a particle belongs to the galaxy. Anyway, if you define the galaxy to include its halo, the galactic disk is not even at the center of the halo, so there's no reason to expect the central black hole to be near the overall center of mass.  

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## 0 answers

