Sources claiming that "M102=M101":

• Pierre Méchain in his 1783 letter to Bernoulli.
• Helen B. Sawyer (Sawyer 1948)
• Owen Gingerich (Gingerich 1960) and Kenneth Glyn Jones (Glyn Jones 1991)
• John Mallas' and Evered Kreimer's Messier Album (Mallas & Kreimer 1978), quoting Gingerich (Gingerich 1960)
• Messier Chart, Messier Poster and other recent products from Sky Publishing Corporation.
• Becvar, see below.
• Before the integration of this article, the SEDS Messier internet database had joint this view; now we have adopted the arguments of the discussion here.

Sources identifying M102 with NGC 5866:

• Pierre Méchain's description matches with NGC 5866, and Charles Messier's handwritten position in his personal copy of the Catalog is almost exactly 5 degrees off NGC 5866 (presumably a data reduction error).
• Camille Flammarion, who had Messier's personal copies of and observing notes related to his catalog, has known Messier's handwritten position, and tentatively identified M102 with NGC 5866 (e.g., Flammarion 1917).
• Harlow Shapley and Helen Davies, in 'The Messier Catalogue', published in PASP Vol. 29 (Shapley and Davies 1917) and also in The Observatory, No. 41 (Shapley and Davies 1918), are also among the first who suggested that M102 could be NGC 5866. They quote a letter from Prof. Bailey:

  Messier's list comprises one hundred and three objects. For all of them, positions are given, except for 102 and 103. For these only the descriptions are given, as follows:

  102. Nebuleuse entre les etoiles Omicron du Bouvier and [sic!] Jota du Dragon; elle est tres-faible; pres d'elle est une etoile de la sixieme grandeur [Nebula betrween the stars Omicron Bootis and Jota Draconis; it is very faint; near it is a star of sixth magnitude].

  103. Amas d'etoiles entre Epsilon et Delta de la jambe de Cassiopeia [Cluster of stars between Epsilon and Delta Cassiopeiae].
  By a star chart, or the sky, you will see that, taken as it stands, no object could be well selected for M102, since Omicron Bootis is too far from Jota Draconis. If, however, Omicron is a misprint for Theta, it becomes intelligible, and M102 is perhaps N.G.C. 5866, altho in Norton's Atlas it is apparently identified as N.G.C. 5979. On our photographs, however, N.G.C. 5866 appears to be the brightest object in this region.

  Shapley and Davis remark that "The visual observations of these neighboring nebulae by the Herschels show N.G.C. 5866 much the brighter, and its identity with M 102 can be accepted as quite probable."
• Don Machholz in his Messier Marathon Observer's Guide (Machholz 1994). Don Machholz also discusses the subject and comes to similar conclusions as the present author.
• Antonin Becvar in his `Atlas Coeli, Atlas of the Heavens - II, Catalogue 1950.0', 1964 gives in the `Anagalactic Nabulae' section for NGC 5866 the alternative name M102 (p. 329 or S21). Oddly, in the `Catalogue of Messier' section on p. 339 or M3, he gives

  M 102 = NGC 5866, Type S [galaxy], [No other data], Notes: `= M 101'

  Perhaps this reflects the situation :-)
• Hans Vehrenberg, in his Atlas of Deep Sky Splendors, claims that Owen Gingerich has added it, which I do not believe because Gingerich (Gingerich 1960) claims the opposite. This claim is possibly based on a report by Paul Ahnert in his Kalender für Sternfreunde 1962, p. 164-166. It seems that this - presumably erroneous - claim also found its way into recent work such as Harvard Pennington's The Year-Round Messier Marathon and George R. Kepple's and Glen W. Sanner's The Night Sky Observer's Guide (Vol. 2).
• RNGC (RNGC, 1973), p. 273, gives M102 as alternative name for NGC 5866.
• Landolt/Börnstein, in their monumental encyclopedia, list NGC 5866 as M102 in their Volume 6, 1, chapter 9, where they have a table of NGC numbers of Messier's galaxies.
• Erich Karkoschka in his Atlas. Karkoschka states in the description to chart N16 (I must translate from the German edition):

  ``Messier's list contains as its object 102 a galaxy [it's the first time I hear that Messier did know that - hf] near the position of NGC 5866. However, his description points to a duplication of M101 [I cannot verify this, see both descriptions given above; my impression is more that NGC 5866 might match the description - hf]. Did Messier do a mistake of 1 hour in right ascension [How, as he gave no measured position :-) - hf] ? Therefore, the designation M102 is nonunique.''

• J.D. Wray, The Color Atlas of Galaxies, Cambridge UP, 1988
• The SIMBAD database has M102 for NGC 5866.
• Tony Cecce in his Twelve Month Tour of the Messier Catalog, May issue.
• A data list from Finland, available on the internet via anonymous ftp: ftp://ftp.funet.fi/pub/astro/dbases/deepsky/messier.dat.
• Nasa's extragalactic database (NED, also telnet ned.ipac.caltech.edu, login ned) had M102 as a name for NGC 5866 until April-May 2001.

Sources with other identifications:

• Admiral Smyth proposes either NGC 5879 or NGC 5866. Kenneth Glyn Jones gives his description:

  `A small but brightish nebula on the belly of Draco with four small stars spreading across field N of it. Doubt as to wether this is the nebula discovered by Méchain in 1781 since Messier describes it as ``very faint'', situated between Omicron Bootis and Iota Draconis. If Omicron Bootis should be Theta Bootis, this is probably the object seen by Méchain and J.H.'s 1910, being the brightest nebula of five in that vicinity.'

  The problem is that John Herschel's number 1910 is NGC 5879, which is however not the brightest of the group; the brightest is NGC 5866.
• Dreyer (NGC) oddly proposes 14th mag galaxy NGC 5928.

                RA (2000.0) Dec (2000) mag   Sp     Id

  23 Theta Boo  14:25:11.8  +51:51:03  4.10v F7V    HR 5404, GC 19467, HD 126660, SAO 29137
  HR 5442       14:32:30.9  +55:23:52  5.76  K5III  GC 19627, HD 128000, SAO 29191
  HR 5451       14:34:16.0  +57:03:55  6.48  F7V    GC 19666, HD 128332, SAO 29202
  HR 5467       14:38:15.2  +54:01:24  5.85  A1V    GC 19742, HD 128998, SAO 29227
  HD 133666     15:03:21.6  +56:02:06  6.86  K2     SAO 29393
  HD 134023     15:05:23.7  +55:40:38  7.5   F8     SAO 29401
* HR 5635       15:06:16.7  +54:33:23  5.25  G8III  GC 20332, HD 134190, SAO 29407
  HR 5715       15:20:05.1  +51:57:31  5.60  A4V    GC 20641, HD 136729, SAO 29487
  12 Iota Dra   15:24:55.8  +58:57:58  3.29  K2III  Edasich, GC 20747, HD 137759, SAO 29520

References:

• Charles Messier, 1781. Catalogue des Nébuleuses et des Amas d'Étoiles. Connoissance des Temps, ou Connoissance des Mouvemens Célestes, pour l'Année bissextile 1784, Paris, 1781, pp. 227-272. Here p. 266 and 267.
• Charles Messier, 1781. Personal copy of his catalog, issues of 1780 (2nd version, M1-M68) and 1781, including manuscript notes. From the library of Camille Flammarion.
  Thanks to Dr. Don Greeley for providing me with a copy of this document!
  Of particular interest here is his manuscript addition of the position of M102 on p. 266 in Messier's personal copy of the catalog of 1781.
• Pierre Méchain, 1783. Extrait No. 9 de la Correspondence de M. Bernoulli. Nouveaux Mémoires de l'Académie Royale des Sciences et Belles-Lettres, année MDCCLXXXII (1782), pp. 46-51 (printed 1784).
• Johann Elert Bode and Pierre Méchain, 1783. Ueber die Bahn des zweyten Kometen von 1781. Entdeckung einiger Nebelsterne; die Elemente der Bahn des neuen Planeten und astronomische Beobachtungen. Von Herrn Mechain, in Paris. Extract from a letter to Mr. Bernoulli dated May 6, 1783. Astronomisches Jahrbuch für das Jahr 1786. nebst einer Sammlung der neuesten in die astronomischen Wissenschaften einschlagenden Abhandlungen, Beobachtungen und Nachrichten. Berlin, 1783, pp. 231-237. Here p. 233.
• William Smyth, 1844. The Bedford Catalogue: From A Cycle of Celestial Objects. John W. Parker, London. Here p. 335.
• John Louis Emil Dreyer, 1895. Index Catalogue of Nebulae Found in the Years 1888 to 1894, with Notes and Corrections to the New General Catalogue. Mem. Roy. Astron. Soc., Vol. 51, pp. 185-228. Here p. 243.
• Guillaume Bigourdan, 1907. Observations des Nébuleuses et d'Amas Stellaires. Chapitre II. Le Découvertes des Nébuleuses. II. De 1700 à W. Herschel. Annales l'Observatoire de Paris. Observations. 1917. pp. E.135-141. Here p. E.140. By the way, Bigourdan only cites Méchain's remark on M102 and does not exploit the letter for Méchain's discoveries.
• Harlow Shapley and Helen Davies, 1917. The Messier Catalogue. Publications of the Astronomical Society of the Pacific, Vol. 29, pp. 177-179 (August 1917) [ADS: 1917PASP...29..177S]
• Harlow Shapley and Helen Davies, 1918. Messier's catalogue of nebulae and clusters. The Observatory, No. 41, pp. 318-320 (August 1918) [ADS: 1918Obs....41..318S]
• Camille Flammarion, 1917. Nébuleuses et Amas d'Étoiles de Messier. L'Astronomie. Revue de la Societé Astronomique de France, November 1917. P. 385-400, here p. 385-386. Also see Flammarion's table of Messier's catalogue online.
• Camille Flammarion, 192x. [Article on M102 in L'Astronomie of c. 1921 - to be consulted.]
• Helen Sawyer Hogg, 1947. Catalogues of Nebulous Objects in the Eighteenth Century. Journal of the Royal Astronomical Society of Canada, Vol. 41, No. pp. 265-273. [ADS: 1947JRASC..41..265S]
• Helen B. Sawyer, 1948. Méchain's additions to Messier's catalogue. Astronomical Journal, Vol. 53, p. 117 [ADS: 1948AJ.....53Q.117S].
• Owen Gingerich, 1953. Messier and His Catalog. Part II. Sky and Telescope, Vol. 12, September 1953, p. 288. Reprinted in Mallas, Kreimer (1978).
• Owen Gingerich, 1960. The Missing Messier Objects. Sky & Telescope, Vol 20, October 1960, p. 196. Reprinted in Mallas, Kreimer (1978).
• Kenneth Glyn Jones, 1968 and 1991. Messier's Nebulae & Star Clusters. 2nd edition, Cambridge University Press, 1991. Practical Astronomy Handbooks Vol. 2. 1st edition 1968, Faber.
• Jack W. Sulentic and William G. Tifft. The Revised New General Catalogue of Nonstellar Astronomical Objects. The University of Arizona Press, 1973.
• John H. Mallas and Evered Kreimer, 1978. The Messier Album. 1st edition. Sky Publishing Corporation, 1978. Second revised printing 1979.
• Don Machholz, 1994. Messier Marathon Observer's Guide - Handbook and Atlas. MakeWood Products, P.O.Box 1716, Colfax, CA 95713, USA.
  Second edition: The Observing Guide to the Messier Marathon. A Handbook and Atlas. Cambridge University Press, 2002.
• Hartmut Frommert, 1995. Messier 102. Posting of May 1995 to Usenet Groups including news:sci.astro.research (May 10, 1995) and Mailing Lists. Copy of the original article.
• Hartmut Frommert, 1998. M102 Controversy. SACNEWS, Issue No. 254, March 1998, pp. 1-5. Available online.
• Hartmut Frommert, 2006. Messier 102: Status der Identifizierung dieses Messier-Objekts. In German. Journal für Astronomie, No. 19 (I/2006), pp. 69-71 (January 2006) [Preprint]

M102 Controversy

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Hartmut Frommert
Christine Kronberg
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Last Modification: March 7, 2006