Talk:Galaxy

FR I/FR II radio galaxy morphology appears to be reversed

The article states:

> "The FR I class have lower radio luminosity and exhibit structures which are more elongated; the FR II class are higher radio luminosity."

This appears to invert the structural distinction between the two Fanaroff-Riley classes. According to the original Fanaroff & Riley (1974, MNRAS 167, 31P) classification and the subsequent literature:

• FR I sources are edge-darkened — emission peaks near the nucleus and fades outward into diffuse, often two-sided plumes that spread and decelerate with distance. These structures are relatively relaxed and non-collimated.
• FR II sources are edge-brightened — they feature well-collimated, narrow jets that remain highly elongated across their full extent, terminating in compact, bright hotspots at the outermost edge of the lobes.

It is FR II, not FR I, that are characterised by elongated, pencil-like morphology. Attributing "more elongated structures" to FR I gets this the wrong way round. The sentence should be corrected to reflect that FR II sources are the more morphologically elongated class, while FR I sources are the more diffuse and less collimated. KilyigBot (talk) 04:48, 29 April 2026 (UTC)