98 



ASTEONOMTCAL PHENOMENA AND' PEOGEESS. 



tanoe a supposition for some time questioned 

 by certain physical explorers appears to be in 

 fair way of receiving an answer in the negative. 

 M. KrQger, it appears, has been employing the 

 excellent heliometer of Bonn upon two stars, 

 one of the 8.9th, and the other of the 9th mag- 

 nitude, in which Argelander had pointed out a 

 large amount of proper motion not less, in the 

 latter case, than 1".2 annually. Thirty-six com- 

 parisons of the former with two other suitably 

 placed stars, yielded a parallax of 0".260 prob- 

 able error, 0".020 ; and forty-five comparisons 

 of the latter in like manner, a parallax of 0".247 

 probable error, 0".021. These results, if con- 

 firmed by future measures, bring those incon- 

 spicuous objects actually nearer to us than Po- 

 laris, Arcturus, or even Sirius ; and a fact of this 

 sort must suggest very remarkable speculations 

 as to the probable structure of the universe. 



Eeference may here be made to Mr. J. "Whar- 

 ton's article (Amer. Jour, of Science, Septem- 

 ber, 1865), entitled, " Speculations upon a pos- 

 sible Method of determining the Distance of 

 certain variably colored Stars," this method 

 depending on an assumed relation of successive 

 colors of the same star to changes in its place, 

 from a perigee to an apogee. 



HerscheVs Catalogue of Nebula and Clusters 

 of Stars. In the year 1864 was published, as 

 the first part of the 154th volume of the " Philo- 

 sophical Transactions of the Eoyal Society," a 

 catalogue of nebulae and clusters of stars, by 

 Sir J. F. "W. Herschel. This catalogue em- 

 braces not less than 5,079 objects, arranged in 

 tabular form, with the right ascension and north 

 polar distance for January 0, 1860, and the an- 

 nual precession in right ascension and north polar 

 distance for 1880, besides ample references and 

 a general description. Of all those objects 

 much the larger number bear- the initials of the 

 Herschels, father and son, having been discov- 

 ered, computed, and catalogued by one or the 

 other of these distinguished astronomers. This 

 publication is opportune, in view of the circum- 

 stance that if the University of Melbourne, 

 Australia, secures a reflector of the highest 

 power, one of its principal uses will be the ex- 

 amination and exact delineation of the numer- 

 ous and wonderful objects of this class presented 

 in the southern hemisphere. The present 

 work includes all the now known clusters and 

 nebula), north and south, so arranged that the 

 observer can at once turn his instrument di- 

 rectly on each, and can tell if he encounters any 

 new object of either class. 



Nebulae. The subject of variability of nebu- 

 la received notice in the volumes of this CYCLO- 

 PEDIA for 1862-'63 ; and certain new questions 

 which the singular phenomena presented by 

 some of these bodies had raised in the minds of 

 astronomers, were there indicated. The results 

 now to be chronicled are of a more definite and 

 (in some respects) also of a more remarkable 

 character. 



Mr. F. Abbott presented to the Eoyal 

 Astronomical Society, November 13, 18G3, a 



paper in relation to the variable star, t) Argus, 

 and the surrounding nebula, the latter of which 

 has been declared the largest and finest in tha 

 southern hemisphere. As the earliest instance 

 of ascertained variation in the appearance of a 

 nebula, he cites the fact of the change detected 

 by Sir William Herschel, 1783-1811, in that 

 surrounding 6 Orionis, which Huyghens had 

 delineated about the year 1656. Eecently, be- 

 sides M. D' Arrest, many other astronomers, in- 

 cluding Bond, Struve, Bouillard, and Pogson, 

 have attested the fact of such changes. 



Sir J. Herschel having, when at the Cape in 

 1838, carefully examined n Argus with an 18- 

 inch reflector, found in its aspect at the time no 

 sign of a resolution into stellar masses ; but he 

 suggests that in extensive nebulas subordinate 

 centres of attraction may become established, 

 and that the whole mass may in time become 

 transformed into a number of discrete bodies, 

 assuming ultimately the condition of a cluster 

 of stars. Mr. Abbott, comparing the Cape de- 

 scription with the appearances detected in pres- 

 ent observations (1863) and especially in view 

 of the fact that the latter are seen by aid of a 

 power no higher than that of a 5-foot achro- 

 maticconcludes that the condition which 

 Herschel had suggested as possible is, in the 

 nebula under consideration, already in part car- 

 ried out. The delineation of 1838 shows with- 

 in the outlines of this nebula a vacant space 

 somewhat in form of a dumb-bell, being com- 

 pressed at the middle, but at the ends sur- 

 rounded by the nebular expansion ; while in the 

 most dense part of the latter was then situated 

 the star, rj Argus. The la'ter observations above 

 referred to show the open space in "the form 

 of a crooked billet, wide in the centre and open 

 at both ends, with y Argus situated within the 

 open space," and here surrounded with what 

 appeared as stars, numerous and brilliant, some 

 of them blue, and others ruddy in color. The' 

 apparent change of place of the star being man- 

 ifestly not a real change in right ascension, the 

 dense portion of the nebula, toward the east, 

 must itself have receded, leaving the star with- 

 out its border, while the ends of the vacant 

 space also became open. Further, while in 

 1838 the star y appeared of the first magnitude, 

 it showed in 1863 only the sixth. 



In a later paper of Mr. Abbott, before the 

 same Society, ho speaks of the " changes that 

 are constantly taking place in the surrounding 

 nebula of rj Argus ; " and he states that every 

 new observation he makes convinces him the 

 more that the whole nebula is breaking up into 

 stars [Mr. Huggins, see below, might say, the 

 appearance of stars]. The form of the open 

 space is now different again from what it was 

 in 1863 ; and the stars surrounding that known 

 as J] present decided colors blue, green, and 

 red, the two former predominating so that 

 the telescope now shows " r) standing out sharp 

 and clear amidst a large field full of richly-col- 

 ored gems, with only a very small patch of 

 nebulous matter."* 



