Very Large Halo Around the Andromeda Galaxy

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    Andromeda Galaxy Halo
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Discussion Overview

The discussion centers on the discovery of a large halo of gas surrounding the Andromeda galaxy, specifically its size and mass compared to previous estimates. Participants explore its implications for understanding galaxy rotation curves and the role of dark matter.

Discussion Character

  • Exploratory, Debate/contested, Conceptual clarification

Main Points Raised

  • Some participants note that the newly discovered halo is significantly larger and more massive than previously thought, raising questions about its potential effects on galaxy dynamics.
  • One participant argues that the halo has little to no impact on gravitational forces affecting stars near the galaxy's center, where rotation curves are typically measured.
  • Another participant expresses initial concern that the halo's increased mass might influence orbital speeds, but acknowledges the halo's diffuse nature as a limiting factor.
  • It is mentioned that despite the halo's mass, there is still a substantial amount of dark matter present, which may dominate the gravitational effects in the region.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the halo's implications for galaxy rotation curves and dark matter, with differing views on its gravitational influence.

Contextual Notes

The discussion highlights assumptions about the halo's density and distribution, as well as the specific regions of the galaxy being considered in relation to rotation curves.

Tanelorn
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Using the Hubble Space Telescope, astronomers have discovered that the immense halo of gas enveloping the Andromeda galaxy is about six times larger and 1,000 times more massive than previously thought.

http://scitechdaily.com/halo-around-the-andromeda-galaxy-is-larger-than-previously-thought/

Would this massive, atmosphere like halo help explain galaxy rotations curves and the need for dark matter?
 
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No, because this halo has little to no impact on the gravitational forces for stars within a few tens of kiloparsecs of the center of the galaxy, which is where rotation curves are measured.
 
ok thanks Chalnoth, I initially thought that being 1,000 times more massive might change the orbital speeds in some way, but as you say it is very diffuse.
 
Yup. As much of this stuff as there is, there's still at least ten times as much dark matter (with a similar distribution).
 

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