Harold Corwin

NGC 4223 = IC 3102 and NGC 4241 = IC 3115. There are several curious things going on here, the least of which are the equalities with the IC numbers!

Here are two galaxies, both seen by both Herschels, yet Dreyer has all but insisted on dropping the NGC number 4223. I'm not really in favor of this at the end of the story -- but we need the story first.

William Herschel found the brightest (H II 137) of the two galaxies on 13 April 1784, placing it "f 11 Virginis 7 min 18 sec, 0 deg 55 arcmin north." As Dreyer noted, these offsets reduce to 12 15 13, +06 58.6 (B1950). William Herschel's second observation, from 28 Dec 1784, reduces to 12 14 49, +07 00.1, which is close to the actual position of the brighter galaxy of the pair. That these observations refer to the same nebula is obvious from William Herschel's note about III 480 (seen only on the second night): "L, vF, would not have been seen if it had not been for the preceding [II 137]." William Herschel's position for the fainter object is also very close to the true position.

John Herschel also has two observations of the brighter galaxy -- his positions are accordant with each other, and with his father's second position. However -- and here is where the confusion sets in -- he calls this brighter galaxy III 480. On his second sweep, he also has an observation of an object which he calls II 137, but of it he says, "pB, R, RA estimated from III 480, which it precedes on the same parallel." All that is true. But the position he gives for this brighter object is a minute of time earlier than it should be -- there is no nebula there. Somehow, John Herschel has got his absolute positions about a minute of time west of the true positions.

John Herschel, of course, used his own positions in GC, and Dreyer copied them into the NGC noting that d'A never saw the preceding of the pair. However, while working on the Scientific Papers, Dreyer looked again at the problem, this time finding that H III 480 is = IC 3115, and that II 137 = NGC 4241 (apparently not noticing that N4241 would also be = IC 3102 in this scenario).

This leaves the number 4223 without a galaxy -- yet William Herschel's observations are very clear that his H II 137 applies to the brighter, western object. This would be NGC 4223. This makes the fainter eastern object III 480 = NGC 4241. All this is in accordance with the numbers in the GC and the NGC itself. The only incorrect data are the RA's which are about a minute of time (NGC 4223) and 30 seconds (NGC 4241) too far west.

This leads me to suggest that the simplest solution is to adopt William Herschel's positions, descriptions, and numbers. The only problem is that the number NGC 4241 has been applied to the brighter galaxy for so long that confusion will undoubtedly result. My feeling is, "So be it."

The IC numbers are unambiguous as Schwassmann's positions are very good. The question of why he did not assign the NGC numbers is pretty clear from the mess above. I would have thought, however, that either he or Dreyer would have caught the equality of the positions for IC 3102 and NGC 4241 (as published in NGC); apparently, neither checked carefully enough, perhaps thrown off by the RA problems.

An addendum: The mess with these two NGC numbers may not be the reason that Schwassmann did not assign them in his list -- he may simply have missed them. There are at least two other NGC/IC equalities in his list: NGC 4235 = IC 3098, and NGC 4246 = IC 3113. There are no big problems with the NGC positions in these cases, yet he has not put the NGC numbers into his list. So, the galaxies also went into the IC. See those IC numbers for a bit more discussion.

― NGC Notes by Harold Corwin

Harold Corwin

IC 3102 = NGC 4223, which see. The IC position is good, so the identity of the IC object is not in doubt. The NGC position, however, is incorrect. See the discussion under NGC 4223 for more on this.

― IC Notes by Harold Corwin

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