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Taking a look at this photo of comet 2I/Borisov and a background galaxy (2MASX J10500165-0152029): 2I/Borisov and background galaxy

And compare it to this rendition of the Milky Way:

Milky Way rendition

The two galaxies slightly resemble each other. Is there a relationship between these two? Was this galaxy used in defining the Milky Way's shape?

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  • $\begingroup$ There are large numbers of known spiral galaxies. Do you know the designation of the particular spiral galaxy in the 2I/Borisov image? $\endgroup$
    – notovny
    Mar 31, 2021 at 14:59
  • $\begingroup$ @notovny The galaxy's designation is 2MASX J10500165-0152029. I've edited my post to include it. $\endgroup$
    – WarpPrime
    Mar 31, 2021 at 15:18
  • $\begingroup$ A photo of the Milky Way, taken from above. Impressive. $\endgroup$
    – ProfRob
    Mar 31, 2021 at 15:53
  • $\begingroup$ @ConnorGarcia I didn't say that its a photo, just a picture. It's definitely a rendition of the Milky Way :) $\endgroup$
    – WarpPrime
    Mar 31, 2021 at 16:57
  • $\begingroup$ @ConnorGarcia I've edited my post to do so. $\endgroup$
    – WarpPrime
    Mar 31, 2021 at 17:26

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In the case of the image of the Milky Way Galaxy that is provided, no.

Wikimedia Commons lists the Milky Way Galaxy image as "Artist's conception of the Milky Way galaxy" and provides the following credit statement, labeling creation date as 25 June 2009:

Nick Risinger - Own work Adapted from the following NASA images: 236084main MilkyWay-full-annotated.jpg Messier51 sRGB.jpg

Given that about 70% of observed galaxies are spiral galaxies, it seems unlikely that 2MASX J10500165-0152029 in particular was specifically chosen to use as a model for formulating the general image of the Milky Way.

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Talking about a "template", I think we need to define what does that means. We do not define a galaxy by using another. We rather categorize the galaxies according to some key parameters from observations.

For a typical non-irregular galaxy, there are several key parameters for describing it: stellar mass, size, stellar color (which is a sort of measurement of its age), and concentration, or put it more general: morphology, etc.

Taking morphology for example. Here is a summary of the SINGS project, which is one of the surveys done for nearby galaxies. You can see the galaxies are nicely categorized into several kinds. The main ones are Ellipticals (usually more massive and old galaxies), barred/unbarred/intermediate Spirals (our Milky Way has a bar).

enter image description here

Talking about the relations, 2MASX J10500165-0152029 has a redshift of z=0.03742. The radius of 2MASX J10500165-0152029 is measured to be about 9 kpc (http://www.sdss.org/dr6/products/catalogs/index.html). It seems comparable with the half-light radius of the Milky Way (~ 6 kpc). However, It's unclear if they have similar stellar mass and colors.

Therefore, I don't think there is a clear link between the two. But you can put them into spirals in general.

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    $\begingroup$ Where are you getting the "radius" measurement for the 2MASS galaxy, and what type of radius measurement is it? (Half-light radius? Exponential scale length? Petrosian radius?) And then: what type of radius measurement are you claiming the Milky Way's is? Are they actually equivalent? $\endgroup$
    – Peter Erwin
    Mar 31, 2021 at 21:14
  • $\begingroup$ Thanks Peter for pointing this out! I should have been more careful with the radius… the definition is a mess… I think you are right. I need to check again the radius of the MW, which may be much smaller if taking the scale length (a few kpc? You certainly have a better idea!). I believe the “textbook value” that I was claiming is from the measurement of the most distant globular clusters. It certainly not compatible to compare directly with the radius of that galaxy. $\endgroup$
    – CyTex
    Apr 1, 2021 at 13:23
  • $\begingroup$ I have Updated the answer to correct the mistake. $\endgroup$
    – CyTex
    Apr 1, 2021 at 13:28

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