Messier 109B (NGC 3953)

Discovered by Pierre Méchain on March 12, 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]

Méchain

(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], but I could not yet determine their positions.

Fortin

1795 [Position marked in Charts 6 and 7; this is Méchain's object]

William Herschel: H V.45 [NGC 3953 = M109B].

V.45. Apr. 12, 1789.
cB. iF. E. mer. LBN. with F. branches 7 or 8' l, 5 or 6' b.
Considerably bright. Irregularly formed. Extended meridionally [along the Meridian, i.e. North-South]. Little brighter Nucleus. With faint brances 7 or 8' long, and 5 or 6' broad.

John Herschel (1833): h 1011 [NGC 3953 = M109B].

h 1011 = H V.45 B; L; vsbM; r; 3' diam. Fine object.
Sweep 328 (February 17, 1831)
Bright; Large; very suddenly brighter to the Middle; round; 3' diameter. Fine object.

Smyth: CCCCXXX [430]. H V.45 [NGC 3953 = M109B].

CCCCXXX [430]. 45 H. V. Ursae Majoris.
AR 11h 45m 25s, Dec N 53d 13'.6
Mean Epoch of Observation: 1838.24 [Mar 1838]
A large pale-white nebula, on the Bear's right haunch, about 1d 1/4 south of Gamma; discovered in April, 1789. It has a peculiar appearance in the field, from there being a coarse small double star north of it, and from its being followed by a vertical line of five equidistant telescopic stellar attendants. This object is fine, but, in my instrument, faintish; it brightens towards the middle; and WH says there is, in that part, an unconnected star, the which I cannot make out.
From every inference this nebula is a vast and remote globular cluster of worlds, for JH assures us it is actually resolvable. By its blazing towards the centre, proof is afforded that the stars are more condensed there than around its margin, an obvious indication of a clustering power directed from all parts towards the middle of the spherical group. In other words, the whole appearance affords presumptive evidence of a wonderful physical fact, -- the actual existence of a central force.

Lord Rosse

[NGC 3953]

John Herschel, General Catalogue: GC 2606 [NGC 3953 = M109B].

GC 2606 = h 1011 = H V.45
RA 11h 46m 27.4s, NPD 36d 53' 3.9" (1860.0). [Right Ascension and North Polar Distance]
cB; L; E 0deg +/-; vsbMLrN. 3 observations by W. & J. Herschel.
Considerably bright; large; elongated in PW 0deg +/-; very suddenly brighter toward the middle where there is a large round nucleus.
Remark: Figure in: P.T. 61 [Lord Rosse 1861], plate xxvi, fig 17.

Dreyer: NGC 3953.

NGC 3953 = GC 2606 = h 1011 = H V.45
RA 11h46m 29s, NPD 36d 53.1' (1860.0). [Right Ascension and North Polar Distance]
cB; L; E 0deg +/-; vsbMLrN [= M109B]. 3 observations by W. & J. Herschel.
Considerably bright; large; elongated in PW 0deg +/-; very suddenly brighter toward the middle where there is a large round nucleus.
Remark: Figure in: P.T. 61 [Lord Rosse 1861], plate xxvi, fig 17.

Gingerich [On the identification of M109]

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

[Only hints for this position are apparent in the author's xerox copy. It is however clearly printed e.g. in Gingerich's article in Sky and Telescope. As stated above, this position is remarkable as the value of the RA coordinate coincides with that of NGC 3953 (M109B), whilest that for the Dec coordinate coincides with that of NGC 3992 (M109). 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 as NGC 3953 - our M109B]

[to come soon]
For now please consult Henk Bril's discussion at: http://www.astrobril.nl/FortinOther.html#M109.