DISCOVERY 



335 



Among the Stars 



A Monthly Commentary 



A Famous Modern Astronomer 



Much of the recent progress in astronomy is associated 

 with the name of Dr. Harlow Shapley, Director of the 

 Harvard College Observatory, Cambridge, Mass., U.S.A., 

 who has within the last few years attained to one of the 

 highest positions in the scientific world. A few biographical 

 notes concerning this distinguished astronomer are there- 

 fore not without interest. Dr. Shapley is a native of 

 Nash\ille, ^Missouri, where he was born on November 2, 

 1885. In 1907 he entered the University of Missouri, 

 where he took the degrees of A.B. and A.M. In 191 1 

 he proceeded to Princeton in order to follow the study of 

 astronomy, and during his tliree years' period of research 

 in the University there he came under the influence of 

 Professor H. N. Russell, and in 1914 graduated Doctor 

 of Philosophy. In 1914 he joined the staff of the Mount 

 Wilson Observatory, and in the same year commenced 

 liis monumental Studies based on the Colours and Magni- 

 tudes in Stellar Clusters. These investigations, of which 

 the results are summarised in the contributions from Mount 

 Wilson Obser\atory, dealt not only with clusters, but 

 with the structure and extent of the visible uni\-erse, the 

 distances of various classes of celestial objects, and 

 problems of cosmogony. In 1921 Dr. Shapley was called 

 to Harvard to succeed Professor E. C. Pickering as 

 Director of the famous Harvard College Observatory. 

 Since his marriage in 1914 he has had the invaluable 

 assistance of Mrs. Shapley, who is herself a distinguished 

 astronomer. 



The Distribution of the Red Stars 



One of the latest of the numerous important circulars 

 issued from Harvard under Dr. Shapley's inspiration 

 deals'^with the distribution of the red stars. These stars 

 were ranked by Secchi in his famous classification as of 

 the third type, and in the Draper Catalogue they are 

 known as Class M. The class is divided into four sub- 

 classes. Ma, Mb, Mc, and Md, and of these the Md stars 

 are the long-period variables. " Practically all the 

 Class M stars in the Henry Draper Catalogue," says Dr. 

 Shapley, " are giants. This conclusion can be reason- 

 ably deduced from what is now knowTi of the relative 

 frequency of giants and dwarfs among stars brighter 

 than the ninth magnitude. The high luminosity of 

 these stars is also e\ident from characteristics of their 

 spectra." The distances of the " invariable class M 

 giants," as Dr. Shapley calls the typical red stars, are 

 easily computed when the apparent brightness is known ; 

 and from the relation between apparent magnitude and 

 distance, it is possible to fix the positions in space of four 

 thousand red giants. Of the stars brighter than the 

 eighth magnitude, Dr. Shapley finds that stars of the 

 sub-class Mi show no concentration to the galactic plane, 

 i.e. are scattered equally over the sky, while the Ma 

 stars are more numerous by 30 per cent, per unit area 

 between galactic latitudes — 10° and + 30° than else- 



where. For stars fainter than the eighth magnitude, 

 both classes Ua and Mb are strongly aggregated towards 

 the plane. This is a highly important result indicating 

 that the fainter stars belong to the Milky Way clouds, 

 while the nearer stars are more or less members of the 

 local cluster. Dr. Shapley also finds that stars fainter 

 than the eighth magnitude are much more numerous 

 in the direction of Sagittarius than in the opposite region 

 of the sky. This may be due to the better quality of the 

 plates used at Arequipa — the southern station of Har- 

 vard College Observatory — for photographing the 

 southern skies. " But it may be largely explained by 

 the greater real depth of the Milky Way in the direction 

 of Sagittarius. The greater frequency in that direction 

 is already established for planetary nebulae, novae, and 

 other types of highly luminous stars." In the case of 

 the long-period variable stars of class Md it has been 

 found that in the direction of Taurus there is but one- 

 half the average number, and in the direction of Sagit- 

 tarius there is twice the average number ; while the 

 fainter stars of the other three sub-classes are much 

 more numerous in the same direction. These results are 

 strongly confirmatory of Dr. Shapley's theory of the 

 structure of the Stellar System, and of his contention that 

 our Solar System is near the centre, not of the general 

 galactic system, but of a local cluster, and that the real 

 centre of gravity of the whole system lies amid the 

 dense star-clouds of Sagittarius. 



The Light Changes of Beta Ceti 



It will be remembered that in the end of February last, 

 Mr. Abbot, a young Englishman resident in Athens, 

 announced that the star Beta Ceti had suddenly increased 

 in brilliance. At the time of the announcement, the 

 constellation Cetus was becoming rapidly invisible in the 

 simset twilight, and confirmation was difficult to obtain. 

 In a paper published in the Monthly Notices of the Royal 

 Astronomical Society, however. Professor A. D. Ross, 

 of Perth, Western Australia, states that his observa- 

 tions under excellent meteorological conditions clearly 

 indicate an increase in brightness. " There can be no 

 doubt," he maintains, "that a remarkable disturbance 

 took place in the star prior to March i." The brightness 

 decreased steadily until March 4, " after which there 

 appear to be fluctuations with a period of about five 

 days." Beta Ceti has never been known to be other 

 than a normal, steady star, and this sudden outburst is 

 extremely puzzling. The star is situated at a consider- 

 able distance from the galactic plane, where outbursts of 

 the kind are relatively frequent. The spectrum of the 

 star is of Harvard type K ; that is to say, it is a yellow 

 star, not very dissimilar to the Sun in physical condition. 



The Recent Solar Eclipse 



Astronomers have been much disappointed by the 

 reports from the various expeditions sent out to observe 

 the total eclipse of the Sun on September 10 last. Pro- 

 fessor Campbell states that the Lick Observatory Expedi- 

 tion was frustrated by a densely clouded sky throughout 

 the whole period of totality. Fifteen other expeditions 



