54 Clusters and Nebulae. 



CLUSTERS AND NEBULAE. — DOUBLE STAR,— 

 GREAT NEBULA IN ORION. — COMPARISON OF 

 SUN AND STARS.— OCCULTATION. 



BY THE KEV. T. W. WEBB, M.A., F.E.A.S. 



8. The Great Cluster near Propus, alias 35 M. Propus is the 

 name given by the ancients to a small star, preceding the foot 

 of the Twin, Castor, as its meaning implies, whose present 

 appearance is so far from warranting any special designation 

 that one might suppose it had declined in brightness. It may 

 be found thus : — A line from £ Tauri to Pollux will be nearly 

 bisected by a considerable 3 mag. star, e Geminorum. Between 

 t, and e will be seen three others, which form a line pointing 

 np. The uppermost and smallest, 5 mag., is Propus, alias 1 

 Geminorum in Flamsteed's nomenclature, being the first star of 

 that constellation as to right ascension comprised in his cata- 

 logue. A little nf from this star the naked eye perceives a 

 faint white cloud, a nebula proper, unnoticed however by the 

 ancients, though they called the head of Orion " stella nebu- 

 losa," and discovered by Messier in 1764. ' The finder shows us 

 a starry nebula, which in the telescope is expanded into what 

 Smyth calls a gorgeous field of stars, from 9 to 16 mags., less 

 rich iii the centre, with a tendency to curved arrangement. It 

 is thus described by Lassell, as viewed with his 24-inch specu- 

 lum, in the Maltese sky, 1852: — "A marvellously striking 

 object. No one can see it for the first time without an excla- 

 mation. Power 160; the field of view 19' in diameter, and 

 angular subtense" (or apparent extent), " 53^, is perfectly full 

 of brilliant stars, unusually equal in magnitude and distribution 

 over the whole area. Nothing but a sight of the object itself 

 run convey an adequate idea of its exquisite beauty. The bril- 

 liancy and concentration of the stellar points and the blackness 

 of the ground cannot otherwise be shown in their just con- 

 trast." The possessors of smaller apertures must of course not 

 expect to witness such a spectacle; yet it is a noble object in 



any telescope. To do justice; to its Wide extent we must em- 

 ploy a very [Q&f power; bul a higher one will best bring out 

 its finest featare, a slightly curved arc or festoon of stars, de- 

 pending, when inverted; and in the eastern sky, from a larger 



oik- at each end. The chord of this arc, which lies n/and sp, 

 Continued for three OT four times its length in the latter direc- 

 tion, will point out a small faint nebula among the outliers of 



the groat cluster, unnoticed in the Bedford Catalogue, but 

 entered in that of Sir \V. Eerschel, where it is 17, VI. ; and in 

 that of Sir J. Ilerschel, who numbers it 375, and calls it " rich, 



