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[M 101]

Messier 101

Observations and Descriptions

Discovered by Pierre Méchain on March 27, 1781.

Messier: M101.
March 27, 1781. 101. 13h 43m 28s (208d 52' 42") +55d 24' 25"
Nebula without star, very obscure & pretty large, of 6 or 7 minutes [of arc] in diameter, between the left hand of Bootes & the tail of the great Bear [Ursa Major]. It is difficult to distinguish when one lits the [graticule] wires. (diam. 7')

William Herschel:
[1784. PT Vol. LXXIV=74 (1784), p. 437-451, here p. 440]
.. To these may added the 1st, 3d, 27, 33, 57, 79, 81, 82, 101 [M101] [of Messier's catalog], which in my 7, 10, and 20-feet reflectors shewed a mottled kind of nebulosity, which I shall call resolvable; so that I expect my present telescope will, perhaps, render the stars visible of which I suppose them to be composed. ..

[Unpublished Observations of Messier's Nebulae and Clusters. Scientific Papers, Vol. 2, p. 660]
1783, Sept. 20. 20 feet, 200. 20 feet, 200. In the northern part is a large [bright] star pretty distinctly seen, and in the southern I saw 5 or 6 small [faint] ones glitter through the greatest nebulosity which appears to consist of stars. Evening bad. This and the 51st [M51] are both so far removed from the appearance of stars that it is the next step to not being able to resolve them. My new 20 feet will probably render it easy.
1789, April 14 (Sw. 921). vB. SN. [very bright, small nucleus] with extensive nebulosity, pretty well determined on the preceding [W] side, but very diffuse to the north following [NE]. Includes the two following nebulae [III.788 and 789, NGCs 5461, 5462], and seems to extend 20', perhaps 30' or more.

John Herschel (1833): h 1744.
h 1744 = M101.
Sweep 347 (May 4, 1831)
RA 13h 57m 9.1s, NPD 34d 48' 40" (1830.0) [Right Ascension and North Polar Distance]
F; vL; R; first g then vsmbM; 5'
Faint; very large; round; first gradually then very suddenly much brighter toward the middle; 5' [diameter].

Smyth: DIII [503]. M101
DIII. 101 M. Bootis [now Ursae Majoris].
AR 13h 57m 31s, Dec N 55d 08'.3
Mean Epoch of the Observation: 1837.26 [April 1837]
"A pale white nebula, in the nebulous field np the right hand of Boötis; it is 5d north-north-east of Alkaid, and a similar distance east-half-south from Mizar. This object was discovered by Mechain in 1781, in whose instruments it was very obscure; and it only exhibited a mottled nebulosity to WH [William Herschel]. Under a very favourable view it is large and well spread, though somewhat faint except towards the center, where it brightens. There are several telescopic stars in the field, one of which is very close to the nebula.
From the nature of this neighborhood, and a trifling uncertainty in the earlier data, this object may be 214 H I [this is actually NGC 5474]; but that astronomer does not appear to have been aware of the identity. It is one of those globular nebulae that seem to be caused by a vast agglomeration of stars, rather than by a mass of diffused luminous matter; and though the idea of too dense a crowd may intrude, yet the paleness tells of its inconceivable distance, and probable discreteness."

Lord Rosse
[PT 1861, p. 681-745, here 729, and drawing on Plate XXIX, Fig. 35]
8 observations. "Sketched 3 times. Mar. 1, 1851. Large spiral; faintish; several arms and knots; 14' across at least. See fig . 35, Plate XXIX." [A table with marked knots and positions follows]

John Herschel, General Catalogue: GC 3770.
GC 3770 = h 1744 = M101.
RA 13h 58m 12.9s, NPD 34d 57' 22.3" (1860.0) [Right Ascension and North Polar Distance]
pB; vL; iR; g, vsmbMBSN. 5 observations by W. & J. Herschel.
Pretty bright; very large; irregularly round; gradually, then very suddenly, much brighter toward the middle, where there is a bright small nucleus.
Remarks: [with GC 3760 = 3766, 3762, 3763, 3764, 3767, 3771, 3773, 3774] h. 1744 = M.101, and its attendents in more or less intimate nebulous connexion. Of those in Lord Rosse's woodcut, PT 1861, p. 729, N, the principle nucleus, is No. 3770 = h. 1774; n1 = No. 3774 = 1744, i; n2 No. 3773 = 1744, h. The others are not lettered, and are made out from the joint evidence of this diagram and the measures of the position and distance of the stars compared with the copper plate, fig. 35 - 1744,a is not improbably = [H] III.787.
Remark: Figure in PT 1861 [Lord Rosse 1861], plate xxix, fig. 35.

Dreyer: NGC 5457.
NGC 5457 = GC 3770 = h 1744; M 101.
RA 13h 58m 14s, NPD 34d 58.6' (1860.0) [Right Ascension and North Polar Distance]
pB, vL, iR, g, vsmbMBSN; = M101
Pretty bright, very large, irregularly round, gradually, then very suddenly, much brighter toward the middle, where there is a bright small nucleus.
Remark: Figure (with GC 3760 = GC 3766 = NGC 5447, GC 3762 = NGC 5449, GC 3763 = NGC 5450, GC 3764 = NGC 5451, GC 3767 = NGC 5453, GC 3771 = NGC 5458, GC 3773 = GC 3778 = NGC 5461, GC 3774 = GC 3779 = NGC 5462) in PT 1861 [Lord Rosse 1861], plate XXIX, fig. 35.

[Descriptions of 762 Nebulae and Clusters photographed with the Crossley Reflector. Publ. Lick Obs., No. 13, Part I, p. 9-42]
NGC 5457, RA=13:59.6, Dec=+54:50. [Publ. Lick Obs.] Vol. VIII, Plate 49. M. 101. This unusually beautiful spiral is about 16' in diameter. There is an almost stellar nucleus, with two bright condensations very close which give a tri-nuclear appearance. The open whorls show a multitude of stellar condensations. [NGCs] 5449, 5450, 5451, 5453, 5455, 5458, 5461, 5462, are simply brighter knots in the great nebula. 10 s.n.
  • Observing Reports for M101 (IAAC Netastrocatalog)

    Hartmut Frommert
    Christine Kronberg

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    Last Modification: May 21, 2006