Milky Way is "in the top percentile of all the galaxies that exist"

  • #26
sophiecentaur
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This is developing into yet another game of Astronomical Top Trumps. There is always some parameter that can put an astronomical object near the top or near the bottom of a list.

The milky way is what it is. Now, if someone could come up with something relevant about whether Galactic size might relate to Alien Civilisations (other than some pro-rata rule) then that could be interesting.
 
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Due to the large discrepancies in the results of the studies about the measuring of the mass of Andromeda and the Milky Way ((a lot) more mass to one, more or less equal mass, (a lot) more mass to the other), shouldn't it be more reasonable and scientific to conclude that until we develop a really solid method of measuring, we don't have a proper scientific answer?
And secondly, with that kind of results all over the place, how is it possible to say (within scientific ground) what are going to be the mass interactions between the two galaxies or if they are going to collide or not? Thanks.
 
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Due to the large discrepancies in the results of the studies about the measuring of the mass of Andromeda and the Milky Way
The Milky Way is uniquely difficult, since as) we are in it, and b) about 85% is obscured by dust.
 
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  • #30
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In any case, the masses of galaxies are highly uncertain due to dark matter. Which, for several purposes, is of limited relevance.
But look at the luminosities of galaxies - AND convert it into multiples of Sun luminosity. The logarithmic magnitude scale is convenient for some purposes, but inconvenient for addition.
Data source is
https://en.wikipedia.org/wiki/List_of_nearest_galaxieslimiting to Local Group, and to galaxies brighter than -15,15... making 100 MSun
  1. Andromeda Nebula - -21,58 - 38 GSun
  2. Milky Way - -20,8 - 18 GSun
  3. Triangulum Galaxy - -18,87 - 3,1 GSun
  4. Large Magellanic Cloud - -17,93 - 1,3 GSun
  5. Small Magellanic Cloud - -16,35 - 300 MSun
  6. M110 - -16,15 - 250 MSun
  7. M32 - -15,96 - 210 MSun
  8. Andromeda VIII - -15,6 - 150 MSun
  9. IC 10 - -15,57 - 150 MSun
  10. Barnard Galaxy - -15,22 - 110 MSun
Now, all 6 galaxies between -15,15 and -17,65 (100 MSun to 1GSun) combined have brightness of 1170 MSun... less than LMC alone. LMC and next 6 combined, at 2,5 GSun, have less than Triangulum alone. Triangulum and next 7 combined, at 5,6 GSun, have less than a third of Milky Way alone. And Milky Way and next 8 combined are dimmer than Andromeda Nebula alone.
Between -15,15 and -12,65 (100 MSun and 10 MSun) there are just 6 Local Group galaxies. I expect they would not significantly alter the results by their number.
 

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