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[M 109]

Messier 109

Observations and Descriptions

Probably discovered by Charles Messier in March or April, 1781.
Independently rediscovered by William Herschel on April 12, 1789.

Messier: M109.
(from the description of M97) A Nebula which is near Gamma UMa.

[According to Owen Gingerich, Messier added a position by hand to his personal copy of the catalog which was identified by Owen Gingerich in 1953 as that of H IV.61 = NGC 3992, which is now called M109. This position is given in Sky and Telescope for September 1953, p. 289, as "11'43=54d.5," or RA=11h 43m, Dec=+54.5 deg (c. 1781.3). In the xerox copy of this catalog owned by the author, this position is almost missing: only suggestions of the two first digits are just readable. This position is strange: RA coincides almost exactly with NGC 3953 (and with Gamma UMa). Dec with NGC 3992.
If Messier actually should have seen NGC 3992, it would be his original discovery, as Méchain almost certainly saw NGC 3953, see below - hf]

(manuscript:) Nebula near Gamma UMa, same right ascension a bit near this star and 1 deg .. more south. Discovered by M. Méchain on March 12, 1781.

[As found by Henk Bril in 2006, this position coincides well with NGC 3953, not NGC 3992. Therefore, we acknowledge this here by assigning that object the designation M109B. We prefer to keep also the name "M109," or if you prefer "M109A," for NGC 3992, first because this is widely used, and second to acknowledge Messier's probable or possible original discovery of this object. - hf]

(in his letter to Bernoulli, May 6, 1783)
Page 265 No. 97 [M97]. A nebula near Beta in the Great Bear. Mr. Messier mentions, when indicating its position, two others, which I also have discovered and of which one is close to this one [M108], the other is situated close to Gamma in the Great Bear [this is M109, or actually M109B], but I could not yet determine their positions.

William Herschel: H IV.61 [NGC 3992].
IV.61. Apr. 12, 1789.
cB. BrN with vFE branches about 30deg np sf. 7 or 8' l, 4 or 5' b.
Considerably bright. Bright resolvable [mottled, not resolved] nucleus with very faint extended branches to position angle 30deg north preceding to south following. 7 or 8' long, 4 or 5' broad.

John Herschel (1833): h 1030 [NGC 3992].
h 1030 = H IV.61.
Sweep 328 (February 17, 1831)
RA 11h 48m 41.3s, NPD 35d 40' 33" (1830.0). [Right Ascension and North Polar Distance]
vB; vL; R; smbM; 3' diam.
Very bright; very large; round; suddenly much brighter toward the middle; 3' diameter.

John Herschel, General Catalogue: GC 2635 [NGC 3992].
GC 2635 = h 1030 = H IV.61.
RA 11h 50m 15.6s, NPD 35d 50' 34.2" (1860.0). [Right Ascension and North Polar Distance]
cB; vL; pmE; sbMBrN. 3 observations by W. & J. Herschel.
Considerably bright; very large; pretty much extended; suddenly brighter to the middle where there is a bright mottled nucleus.

Dreyer: NGC 3992.
NGC 3992 = GC 2635 = h 1030 = H IV.61.
RA 11h 50m 19s, NPD 35d 51.3' (1860.0). [Right Ascension and North Polar Distance]
cB, vL, pmE, sbMBrN; = M109
Considerably bright, very large, pretty much extended, suddenly brighter to the middle where there is a bright mottled nucleus.

[Descriptions of 762 Nebulae and Clusters photographed with the Crossley Reflector. Publ. Lick Obs., No. 13, Part I, p. 9-42]
NGC 3392, RA=11:52.4, Dec=+53:55. A beautiful, slightly oval spiral 7' in length. Bright, almost stellar nucleus; whorls are rather open and show a number of faint condensations; the central portions show signs of Phi-type formation [the bar]. 20 s.n.

Gingerich [On the identification of M109]
[..] following this [the printed description of M97], Messier has written in the position of NGC 3992. [..]

[This position is not apparent in the author's xerox copy. If Messier actually observed NGC 3992, it would have been his personal, original discovery - hf]

Although Flammarion found Messier's notation of the position of the nebula near Gamma Ursae Majoris [..] he made no attempt to number it, and because Méchain did not give precise positions, Dr. Hogg omitted identifications of this and the other nebula near Beta Ursae Majoris. From my study of this region, the nebula near Beta is unambiguously NGC 3556, while an examination of the critical limiting magnitude of the catalogue indicates that the one near Gamma must be NGC 3992, a fact confirmed by the position Messier added to his personal copy. Thus, if the objects from M104 to M107 are included, it seems logical to me to number NGC 3556 and NGC 3992 as M108 and M109 respectively, especially as they are mentioned in the original catalogue.

[While exactly so for M108, the limiting magnitude of the Messier objects would allow for another identification: NGC 3953 of mag 10.1. A closer look at the position mentioned in Messier's manuscript notes suggests this latter identification more than that with NGC 3992.]

Bril [New identification of M109]
[to come soon]
For now please consult Henk Bril's discussion at: http://www.astrobril.nl/FortinOther.html#M109.
  • Observing Reports for M109 (NGC 3992) (IAAC Netastrocatalog)

    Hartmut Frommert
    Christine Kronberg

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    Last Modification: January 6, 2021