Talk:Perseus Arm

message: I think the last bit of the first para is missing some words. Should'nt it say "...the long bar at the center of the milky way"?JWorkman 20:59, 3 January 2013 (UTC)
thread_title:  Words missing? 

message: "It is named after its proximity to the constellation Perseus." -This is really unclear and needs both rephrasing and sourcing. The area of a constellation does not match any discrete field or pocket of 3-D space, of the Milky Way. Strictly speaking the constellations only exist on the handbook maps we make of the sky, not as any depth part of space or of the Milky Way. You can measure a distance to a given star, but not even a mean distance to a given constellation; the area on the star map that's tagged "Cygnus" or "Pisces" will contain hundreds of thousands of stars and as bodies they are unrelated. 
And 98% of the individual stars we can see with the unaided eye, lie within perhaps 3.000 light years, which means nearly all of them are in the Orion Arm, where the sun itself is located. The main stars of The Perseus constellation would be Orion arm stars too. So if the name "Perseus arm" refers to anything in the constellation Perseus, it's likely to be a nebula, a radio source or something of the kind, some single object of a more distant kind.83.254.151.33 (talk) 00:20, 28 August 2013 (UTC)
replies: text: Ok, I clarified that statement. Ruslik_Zero 06:17, 28 August 2013 (UTC)
thread_title:  Name 

message: In the third paragraph of the section "Overview," the Perseus arm is said to have "length of more than 60,000 lr and the width of about 1,000 lr..."  The reference given makes no use of such a unit, nor does it turn up in a web search.  Looking at the reference (a PDF is available at the link provided by the DOI), a direct statement of the dimensions given is not apparent, but the diagram used repeatedly in the discussions, with dimensions in kilo parsecs (kpc) bears out the length and width numbers for the Perseus arm given here.  I'm no expert, so I didn't edit the Article.  Comments? -- motorfingers : Talk  05:29, 11 March 2022 (UTC)
replies: text: Looks like a typo.  Edits were made by this user.  When comparing the edits to their other edits in their contribution history, it becomes clear that they mistyped "ly" for light year. Viriditas (talk) 08:29, 11 March 2022 (UTC)
replies: text: I thought of that, but a kpc is 3,262 light years.  I need to take a look at the article's Reference 3 and take some more time, absent a subject-matter expert to resolve that.  A first look tonight, estimating the length of the Perseus arm, I can't get close to a length of 60,000 light-years or a thickness of 1,000 light-years.  A general search on "Perseus arm length" with DuckDuckGo produces a 2022 reference that heavily uses our Reference 3 as his reference 2009b, that gives the thickness of the Perseus arm as about 63pc, or about 205 light-years.  This reference's Figure 7 gives a length for the Perseus arm of about 12,000 pc or 39,000 light-years.  This reference's Figure 13 shows about the vertical width (not a radial width) of about 200 pc or 650 light-years at several points over its length. -- motorfingers : Talk  12:24, 11 March 2022 (UTC)
replies: text: You can revert their edits in the page history or rewrite them. Viriditas (talk) 20:43, 11 March 2022 (UTC)
thread_title:  The unit "lr" used to give size of the Perseus Arm Appears to be kpc