Is Dark Matter Present in the Milky Way Galaxy?

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Discussion Overview

The discussion revolves around the presence of dark matter in the Milky Way galaxy and its implications for the solar system. Participants explore theoretical aspects, observational evidence, and the characteristics of dark matter in relation to baryonic matter within the galaxy.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants question whether dark matter is present in the Milky Way or the solar system, suggesting that the solar system may have less dark matter than expected.
  • One participant asserts that the Milky Way contains approximately 80% dark matter and 20% baryonic matter, although this is challenged by a correction regarding the terminology used.
  • Another participant suggests that dark matter is necessary for the structural integrity of the Milky Way, implying that without it, the galaxy would not hold together.
  • A reference is made to a calculation regarding dark matter mass in the solar system, indicating a limit on its concentration within Saturn's orbit.
  • One participant argues that dark matter cannot form clumps the size of the solar system due to the high average velocity of dark matter particles, suggesting that if it could, the observable universe would exhibit different characteristics.

Areas of Agreement / Disagreement

Participants express differing views on the presence and characteristics of dark matter in the Milky Way and the solar system, indicating that multiple competing perspectives remain unresolved.

Contextual Notes

There are limitations regarding the assumptions made about dark matter's distribution and its effects on galactic structure, as well as the dependence on observational data that may not fully capture the complexities of dark matter interactions.

Tony Stark
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Is the presence of Dark Matter noted in Milky Way or somewhere around solar system??
 
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Tony Stark said:
Is the presence of Dark Matter noted in Milky Way or somewhere around solar system??
I remember seeing (sorry, no citation) something about our solar system having a paucity of dark matter relative to what was believe to be likely. The milky way, as far as I know, is a normal galaxy and has about 80% dark matter, 20% boronic matter just like other galaxies.
 
I believe you meant 20% baryonic matter
 
jimgraber said:
I believe you meant 20% baryonic matter
Knowing me, I probably meant moronic. :smile:
 
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If it didn't then it would've probably could not have held together also considering that the Milky Way can be small compared to other galaxies, so the answer to that would possibly be yes, or else it wouldn't hold together.
 
The best credible recent calculation for dark matter mass in the solar system appears to be http://arxiv.org/abs/1306.5534, Constraints on Dark Matter in the Solar System, where it is asserted "The dark matter mass in the sphere within Saturn's orbit should be less than 1.7 × 10-10 M ⊙ even if its possible concentration is taken into account." To put this into perspective Earth's mass is about 3 × 10-6 M ⊙,
 
Dark matter cannot form clumps (density inhomogeneities) the size of the solar system - average velocity of DM particles is too large for that.

We know that because if DM would be capable of doing that, the galaxy would look very different. For one, we'd see a large number of multiple star systems with "unseen mass" (IOW: systems where stars orbit way too fast). At least several percent of all multiple systems would show such effect. This is not observed.
 

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