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NGC 7646 (17,808 of 18,816)

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NGC 7646

NGC 7646, IC 5318, LEDA 71338, MCG-02-59-015

RA: 23h 24m 6.8s
Dec: −11° 51′ 37″

Con: Aquarius
Ch: MSA:1328, U2:304, SA:17

Ref: SIMBAD, NGC/IC

(reference key)

Type: galaxy, Sc

Mag: B=14.7, V=14

Size: 0.9′ x 0.6′
PA: 135°

History and Accurate Positions for the NGC/IC Objects (Corwin 2004)

NGC 7646, which may be = IC 5318, is another of the Leander-McCormick nebulae found by Muller, with its discovery announced before a decent position was available. Muller's description (magnitude = 14.5, diameter = 0.2 x 0.1, extended 260 deg) would fit IC 5318 if he saw only the bar of the galaxy. He also has a "*9, PA 10 deg, distance 3.6 arcmin." The star is actually 3.8 arcmin away at PA = 346 deg. Did Muller somehow get his PA into the wrong quadrant? (There is no sketch to help us in this case).

The main thing that makes me question the identification is the star of magnitude 9 or 10 superposed on the galaxy. Muller surely would have mentioned the star had he noticed it -- since the nature of the nebulae was still in debate in the late 1880's, nearby stars were often taken as possibly physically associated with the nebulae.

IC 5318 was found by Herbert Howe, using Chamberlain Observatory's 16-inch refractor. He measured the position of the galaxy, and noted the superposed star but, because of Muller's poor position, did not make a connection with the NGC number. Given the problems with Muller's position and description, we should perhaps simply note the possibility of the identity, and let it go at that.

Published comments

Sulentic & Tifft (1973)

The RNGC (Sulentic and Tifft 1973) notes that this is a galaxy. Their coded description reads S,UHISB,*TIP NP ARM.

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