48 



ASTRONOMICAL PHENOMENA AND PEOGEESS. 



proximity of the nebulous matter, so that, 

 when the doubtless systematic motions of that 

 matter bring it again into the star's neighbor- 

 hood, Eta Argus will resume its ancient splen- 

 dor? May it not be that the sun is affected in 

 like manner, though to less extent, by the 

 motions of those cometic and meteoric sys- 

 tems which circle around him ? Some of these 

 systems pass very near him, and many of them 

 may be so related to the planetary motions as . 

 to be subject to periodic variations of orbital 

 motion. Even others, such as the system cor- 

 responding to the November meteors, though 

 now obviously not associated with the solar 

 changes, may have their motions so changed 

 as at some future epoch to generate solar 

 spot-periods. Eemembering how enormous 

 must be the number of meteoric systems cir- 

 cling round the sun, little doubt can exist that 

 meteors must fall upon his body in countless 

 millions. Indeed, it has been thought not un- 

 worthy of credit, even by so exact a man of 

 science as Professor Tyndall, that the whole of 

 that supply of heat and light which the sun 

 pours forth unremittingly to the worlds cir- 

 cling around him may be generated by the con- 

 tinual downfall of meteoric masses upon the 

 solar surface ; so that any disturbance of the 

 meteoric motions must importantly affect the 

 condition of that luminary." 



Star-drift of the Central Sun. Upon inves- 

 tigating the proper motions of the stars in 

 Gemini, Cancer, and Leo, Mr. B. A. Proctor 

 has found a community of motion more strik- 

 ing than that noticed by Madler in Taurus, and 

 regards the great double cluster in Perseus as 

 far more likely to be an important centre of 

 motion than the Pleiades, of which Alcyone 

 had been named by Madler as most probably 

 the central sun of our sidereal system. Mr. 

 Proctor remarks that Madler required a star 

 on the Milky Way as the centre of the galaxy, 

 and Alcyone does not lie on the Milky Way, 

 and also that he required this centre to lie 90 

 from the apex of the solar motion, which is 

 not the case with Alcyone ; but that the great 

 cluster in Perseus fulfils both these conditions 

 in the most perfect manner. The author says 

 that these particular instances of star-drift are 

 not the less remarkable ; that the stars are 

 drifting almost exactly in the direction due to 

 the proper motion assigned to the sun. because 

 the recent researches of the Astronomer Eoyal 

 have abundantly proved that the apparent 

 proper motions of the stars are not to be rec- 

 ognized as principally due to the sun's motion. 

 " Mr. Stone has shown even that we must as- 

 sign to the stars a larger proper motion, on 

 the average, than that which the sun possesses. 

 Looking, therefore, on the stars as severally in 

 motion, with velocities exceeding the sun's on 

 the average-, it cannot but be looked upon as 

 highly significant that in any large region of 

 the heavens there should be a community of 

 motion such as I have described. We seem 

 compelled to look upon the stars which exhibit 



such community of motion as forming a dis- 

 tinct system, the members of which are asso- 

 ciated indeed with the galactic system, but are 

 much more intimately related to each other. 

 In other parts of the heavens, however, there 

 are instances of a star-drift opposed to the 

 direction due to the solar motion. A remark- 

 able instance may be recognized among the 

 seven bright stars of Ursa Major. Of these, 

 five are all drifting in the same direction, and 

 almost exactly at the same rate toward the 

 'apex of the solar motion,' that is, the point 

 from which all the motions due to the sun's 

 translation in space should be directed. If 

 these five stars, indeed, form a system (and I 

 can see no other reasonable explanation of so 

 singular a community of motion), the mind is 

 lost in contemplating the immensity of the 

 periods which the revolutions of the compo- 

 nents of the system must occupy. Madler had 

 already assigned to the revolution of Alcor 

 around Mizar a period of more than 7,000 

 years. But if these stars, which appear so 

 close to the naked eye, have a period of such 

 length, what must be the cyclic periods of the 

 stars which cover a range of several degrees 

 upon the heavens?" There are many other 

 interesting cases of the same kind. 



Nature, commenting on Mr. Proctor's theory, 

 remarks that the star-drift described by him 

 serves to explain several phenomena which had 

 hitherto been thought very perplexing. In the 

 first place, it accounts for the small effect 

 which the correction due to the solar motion 

 has been found to have in diminishing the 

 sums of the squares of the stellar proper mo- 

 tions. Again, it explains the fact that many 

 double stars, which have a common proper 

 motion, appear to have no motion of revolution 

 around each other ; for clearly two members 

 of a drifting system might appear to form a 

 close double, and yet be in reality far apart 

 and travelling, not around each other, but 

 around the centre of gravity of the much 

 larger system they form part of. While map- 

 ping the proper motions of the stars, Mr. 

 Proctor has been led to notice that the rich 

 cluster around Chi Persei falls almost exactly 

 on the intersection of the Milky Way with the 

 great circle which may be termed the equator 

 of the solar motion ; that is, the great circle 

 having the apex of the sun's motion as. a pole. 

 This circumstance points to that remarkable 

 cluster, rather than to the Pleiades, as the 

 centre of the sidereal system, if indeed that 

 system has a centre cognizable by us. When 

 we remember that for every fixed star in the 

 Pleiades there are hundreds in the great clus- 

 ter in Perseus, the latter will seem the worthier 

 region to be the centre of motion. The author 

 is disposed, however, to regard the cluster in 

 Perseus as the centre of a portion of the sidereal 

 system, rather than as the common centre of 

 the galaxy. 



Heating-power of the Stars. In the proceed- 

 ings of the Eoyal Society for January, 1870, 



