Andromeda vs. Milky Way galaxies

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Discussion Overview

The discussion revolves around the comparative characteristics of the Andromeda and Milky Way galaxies, focusing on their sizes, masses, and the implications of their upcoming collision. Participants explore various aspects of galaxy formation, structure, and the dynamics of galactic mergers.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants question why Andromeda is larger in diameter yet has a lower mass compared to the Milky Way, suggesting it may be a Low-Surface Brightness (LSB) galaxy.
  • There is speculation that the Mass-Radius Relation could be affected during galaxy collisions and mergers.
  • Concerns are raised about the reliability of the mass and diameter figures presented, with some arguing that the error bars in measurements are significant and should not be ignored.
  • One participant suggests that the visibility of Andromeda may be influenced by its contrast against the dark background, rather than its actual size.
  • Discussion includes the dynamics of the upcoming merger, with some arguing that the Milky Way's greater density may lead to it distorting less than Andromeda during the collision.
  • Participants note that actual star-star collisions will be rare during the merger, but significant deflections of stellar orbits are expected.
  • There is speculation about the implications of dark matter in the mass calculations of both galaxies, questioning whether the Milky Way has more dark matter than Andromeda.
  • Some participants discuss the potential for increased star formation rates during the merger, despite the rarity of direct star collisions.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the characteristics and dynamics of the Andromeda and Milky Way galaxies. There is no consensus on the implications of their size and mass differences, nor on the reliability of the data presented.

Contextual Notes

Limitations include the reliance on potentially inaccurate mass and diameter figures, the complexity of measuring galaxy characteristics, and the unresolved nature of the effects of dark matter on these measurements.

  • #31
I don't know about that. See, I'd count cosmology as being in the high-precision bucket. Especially since I tend to think of CMB data as its cornerstone, more so than anything local.
Anyhow, last time I heard Reiss give a talk (online, not in person), it was a CfA colloquium about getting the precision of local H0 measurements down to 1% or something. He did mention the systematic issue with different instrument being used to collect data for same SNIa events, but in the context of past practices as opposed to his team's current effort.
But then again, I have no hands-on knowledge on how the sausage is made.
 

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