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[M 102]

Messier 102 (NGC 5866)

Observations and Descriptions

Discovered probably in March or April 1781 by Pierre Méchain, or little later in 1781 by Charles Messier.
Independently discovered by William Herschel on May 5, 1788.

Messier: M102.
[March/April 1781]. 102. [Méchain]
Nebula between the stars Omicron [actually Theta] Bootis & Iota Draconis: it is very faint; near it is a star of the sixth magnitude.
(Handwritten position added by Messier in his personal copy: 14h 40m, +56.)

[This position matches well with the position of NGC 5866, if one takes an error of exactly 5 degrees (20 min) in right ascension into account.]

(in his letter to Bernoulli, May 6, 1783; disclaimer of the discovery and claim it was an erroneous reobservation of M101)
I will add only that No. 101 & 102 on the p. 267 of the Connoissance des tems [for] 1784 are nothing but the same nebula, which has been taken for two, by an error in the [sky] charts.

[Bode has worked this up for publication in the Astronomisches Jahrbuch for 1786:]
On page 267 of the "Connoissance des Temps for 1784" M. Messier lists under No. 102 a nebula which I have discovered between Omicron [actually Theta] Bootis and Iota Draconis; this is a mistake. This nebula is the same as the preceding No. 101. Mr. Messier, caused by an error in the sky charts, has confused this one in the list of my nebulous stars communicated to him.

[However, his description (given above) matches well with an existing object, NGC 5866, as does Messier's position measurement given above, up to the data reduction error. This issue was ever since, and is still, subject to controversial discussion. Anyway, M102 was missed for more than a century.]

William Herschel: H I.215.
I.215. May 5, 1788.
vB. cL. E. f. 2 st.
Very bright. Considerably large. Extended [elongated]. Following [lying east of] 2 stars.

[1811: PT Vol. 1811, p. 226-336; here p. 294]
14. Of extended Nebulae.
This class of nebulae, which are chiefly extended in length, but at the same time have a considerable breadth, is very numerous. I have devided the nebulae it contains, which are 284, into five assortments as follows. (*)
(*) [Second assortment] Sixty-two extended nebulae of various large sizes [including H I.215 = NGC 5866]

John Herschel (1833): h 1909.
h 1909 = I.219 [actually I.215].
Sweep 144 (April 13, 1828)
RA 15h 1m 47.1s, NPD 33d 34' 40" (1830.0) [Right Ascension and North Polar Distance]
vB; pmE; gbM; 50" l, 20" br; pos 326.0 by microm.
Very bright; pretty much elongated; gradually brighter toward the middle; 50" long, 20" broad; extended along position angle 326 [= 146] by micrometer.

Smyth: DXXXI [531]. H I.219 [actually H I.215]
DXXXI. 219 H. I. Draconis.
AR 15h 02m 03s, Dec N 56d 23'.0
Mean Epoch of the Observation: 1837.60 [August 1837]
A bright-class oval nebula, under the body of Draco, with its major axis tending towards the vertical of the np and sf quadrants. It is rather faint at the edges, though not so as to obscure the form. It was discovered by WH in March, 1789 [this was H I.219 = NGC 3665; WH cataloged H I.215 on March 5, 1788], and is No. 1909 of his son's Catalogue [where the error "219" first occurred]. There is a small star nearby above it, and three larger more distant, of which the preceding is coarsely double. The mean place is differentiated with Theta Draconis; from which it lies 7 deg to the west-south-west, or one-third of the distance towards Alkaid.

DXXXIII [533]. M 22? [actually M102?]
DXXXIII. 22 M. (?) Draconis.
AR 15h 04m 50s, Dec N 57d 36'.1
Mean Epoch of the Observation: 1835.52 [July 1835]
[this object is NGC 5879 (H 2.757, h 1910, GC 4064)]
A small but brightish nebula, on the belly of Draco, with four small stars spreading across the field, north of it. There may be a doubt as to whether this is the nebula discovered by Méchain in 1781, since Messier merely describes it as "very faint," and situated between Omicron Boötis and Jota Draconis. But there must be some mistake here; the one being on the herdman's leg, and the other in the coil of the Dragon far above the head of Boötes, having 22 deg of declination and 44' [44 min] of time [in RA] between them, a space full of all descriptions of celestial objects. But as the Theta in the raised right hand of Boötes, if badly made, might be mistaken for an omicron, this is probably the object seen by Méchain, and JH's 1910 [NGC 5879]; it being the brightest nebula of five in that vicinity [actually, the brightest is NGC 5866]. A line from Kappa in Draco's tail, led to the south-east of Thuban, and prolonged as far again, strikes upon its site.

Lord Rosse
[Phil. Trans. 1850, p. 499-514, drawing on Plate XXXVII, fig. 8]
Plate XXXVII, fig. 8, H. 1909. - "April 27, 1848. - A very bright resolvable [mottled] nebula, but none of the component stars to be seen distinctly even with a power of a thousand. A perfectly straight line and longitudinal division in the direction of the major axis. Resolvability most strongly indicated toward the nucleus.
"May 2, 1848. - Not seen so well as on April 27. Darkness in the middle, along the major axis, barely visible.
"April 1849. - A long ray elliptical. Major axis perhaps eight times minor axis: night indifferent: at intervals a few stars faintly perceptible."
[Phil. Trans. 1861, p. 681-745, here p. 731] 8 observations. "April 13, 1850. vB; oval; E np, sf; * in np end. "Nova" near; vS."
Very bright; oval; extended north-preceding [NW] to south-following [SE]; star in north-preceding [NW] end. "New Nebula" nearby, very small.

H.I 215. H., very bright. D'A., 90"x30".
Espin: Not gaseous.

John Herschel, General Catalogue: GC 4058.
GC 4058 = h 1909 = H I.215.
RA 15h 2m 36.3s, NPD 33d 41' 39.4" (1860.0) [Right Ascension and North Polar Distance]
vB; cL; pmE 146.0 deg; gbM. 2 observations by W. & J. Herschel.
Very bright, considerably large, pretty much extended along position angle 146 deg, gradually brighter toward the middle.
Remark: Figure in PT 1850 [Lord Rosse, 1850], plate xxxvii, fig. 8.

[Further Observations on the Spectra of some Nebulae, with a Mode of determining the Brightness of these Bodies. Phil. Trans. Roy. Soc., Vol. 156 (1866), p. 381-397; here p. 389]
[No. [GC] 4058. 1909 h. 215 H. I. R.A. 15h 2m 36s.3. N.P.D. 33d 41' 39".4. Very bright; considerably large; gradually brighter in the middle.]
"None of the component stars to be seen. Resolvability strongest near nucleus." - Lord Oxmantown [Rosse]
Spectrum continuous.

Dreyer: NGC 5866.
NGC 5866 = GC 4058 = h 1909 = H I.215.
RA 15h 2m 39s, NPD 33d 41.7' (1860.0) [Right Ascension and North Polar Distance]
vB, cL, pmE 146deg, gbM; = M102?
Very bright, considerably large, pretty much extended along position angle 146 deg, gradually brighter toward the middle.
Remark: Figure in PT 50 [Lord Rosse, 1850], plate XXXVII, fig. 8.

In the appendix to his first IC catalogue of 1895, Notes and Coorections to the New General Catalogue, Dreyer supposes that M102 may be NGC 5928:
NGC 5928. This is possibly Messier 102, found by Méchain: "Nébuleuse entre les étoiles Omicron du Bouvier et Iota du Dragon: elle est très foible; pres d'elle est une étoile de la sixieme grandeur." I assume that Iota Draconis is an error for Iota Serpentis.
[This assumption can be waived as NGC 5928 is of only 14th magnitude and thus much to faint for Messier's and Méchain's instruments - hf]

Camille Flammarion (1917):
[in his List of the Messier Objects published in L'Astronomie, November 1917, p. 394-395, Flammarion identifies M102 with NGC 5866]
   Dates      No.   NGC  Position (Messier)   Position 1900    Constellations
    of                                                               and
Observation   (M)           RA        Dec        RA    Dec       Description

- 102 5866? 14.40. 0 +56 15. 3.8 +56. 9 Ursa Major. Spiral Nebula.

Harlow Shapley and Helen Davies: On the identification of M102
[in PASP 29, No. 170, p. 177 (1917)] "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."

[Descriptions of 762 Nebulae ans Clusters photographed with the Crossley Reflector. Publ. Lick Obs., No. 13, Part I, p. 9-42]
NGC 5866, RA=15: 3.7, Dec=+56: 9. [Publ. Lick Obs.] Vol. VIII, Plate 51. Very bright, 3'x1' in p.a. 125deg. No spiral structure is discernible, but it appears to be a spiral of the Andromeda type seen edgewise. Its most striking feature is a narrow, clear-cut dark lane along the middle, marking a slight angle with the major axis. See Abs. Eff. 37 s.n.

Helen B. Sawyer [Hogg]: Remarks on the identification of M102
[in Astronomical Journal, Vol. 53, p. 117 (1948)] ".. a long-overlooked letter by Pierre Méchain was found in Bode's Jahrbuch for 1786. .. Méchain says that the nebula Messier 102 does not exist; it was an error. (A number of astronomers have spent time trying to identify this as the spiral NGC 5866.) .."

Sullentic/Tifft, RNGC: NGC 5866.
Bright elliptical-like, elongated, brighter toward center, diffuse halo
Gives "M102" as cross reference.
  • Observing Reports for M102 [and NGC 5866] (IAAC Netastrocatalog)

    Hartmut Frommert
    Christine Kronberg

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    Last Modification: January 3, 2005