Talk:Cygnus X-1

No hair theorem

The article states that "the no hair theorem guarantees that black holes do not have magnetic poles". However, the no hair theorem actually says that black holes are completely specified by mass, charge, and angular momentum. If the black hole has charge and angular momentum, that defines a magnetic pole--it's enough to write the entire Faraday tensor, which includes both electric and magnetic fields.Mpalenik (talk) 22:25, 9 January 2017 (UTC)

@Mpalenik Also, isn't the no-hait theorem a THEORY? As such, it can't GUARANTEE that the magnetic field is aligned as the article states - only predict, right? Mastakos (talk) 08:25, 4 March 2025 (UTC)

well, It is a theory, but is the best theory we currently have on the subject. By that logic, general relativity is a theory too ~2026-10236-13 (talk) 12:56, 15 February 2026 (UTC)

New mass measurement

Miller-Jones et al. (2021) give a larger distance measurement of 2.22+0.18
−0.17 kpc thus a greater black hole mass of 21.2±2.2 M_☉: "Cygnus X-1 contains a 21–solar mass black hole—Implications for massive star winds" Nrco0e (talk · contribs) 19:36, 19 February 2021 (UTC)

Astrometry data and sources [1],[2]

Hey. I'm in the process of translating this page for the Hebrew Wikipedia as part of a university course, and I'm going over some sources regarding the Astrometry of Cygnus X-1. This page cites the proper motion values as

RA: −3.37[1] mas/yr Dec.: −7.15[1] mas/yr

With both values seemingly coming from source [1], "Validation of the new Hipparcos reduction- Floor van Leeuwen". Now, I looked over this source and couldn't find any data regarding the proper motion values (or anything else, for that matter) for Cygnus X-1 under any of its aliases. I might be reading the data wrong- It should be noted that I'm no expert in astronomy, just an amateur- But a simple attempt at matching numbers and names results in no matches.

There's also source [2], which claims different values for the proper motion, at -3.882 -6.171 [0.048 0.054 90] mas/yr. This discrepancy, in my view, is problematic.

What do you think? Should the info and sources in this page be changed? OmerDavidSegal (talk) 11:59, 1 April 2021 (UTC)

Mass: sidebar vs lead

In the lead, the article says the mass of Cygnus X-1 is about 21.2 times our solar mass. However, in the sidebar under details, it instead lists the mass as 13.8 to 17.5 +2/-1 solar masses. So which is correct? MrAureliusR_{Yell at me!} 11:55, 11 April 2026 (UTC)