Januaky, 1902.] 



KNOWLEDGE 



the stai-s. CerUiinly there is nothing to suggest a dog 

 in tlio presence of two fairly bright stai-s some five 

 dc^-ecs apart. 



The Greater Dog is a far- fuller constellation. Beta 

 precedes Sirius some twenty-two minutes and is therefore 

 called Miu'zim, the " Announcer.' Quite low down near 

 our horizon is a right-angled triangle of bright stais, 

 the right angle being marked by Delta. Ejjsilou and 

 Eta at the two other points of the triangle lie some 

 three degi-ees further south and are nearly on the same 



The Midniglit Skv for T-ondon, 1902, Januarv. 



parallel with each other; Epsilon is Adhara, the " back." 

 Delta is in the centre of a very interesting region, a 

 curious curve of small stars preceding it, whilst another 

 follows. 



Argo is scarcely at all an English constellation, the 

 gi-catcr part of its huge bulk lying below our horizon. 

 The vessel is drawn in our atlases and described by 

 Aratus as travelling stem foremost. Thus in Brown's 

 translation we read : — 



" Stern forward Argo by the Great Dog's tail 

 Is drawn ; for her's is not a usual course. 

 But backward turned she comes, as vessels do 

 When sailors have transposed the crooked stern 

 On entering harbour ; all the ship reverse. 

 And gliding backward on the beach it grounds. 

 Stem forward thus is Jason's Argo drawn." 



The Greek legend of the voyage of the Argonauts 

 under Jason to recover the Golden Fleece was believed 

 by Sir Isaac Newton to have an actual historical basis, 

 and to record the beginning of Greek commerce. In 

 fact in his view the constellations generally were 

 designed by the Greeks to celebrate the heroes and deeds 

 of this gi-eat expedition. The knowledge which later 

 times have brought us have compelled us to recognise 

 that the constellations are far older than Newton thought 

 them, and beyond a doubt Proctor was quite correct in 

 recogTiising in Argo and the southern constellations near 

 it, — Centaurus, who is represented as having apparently 

 just left the ship and the Altar at which he is 

 sacrificing, — a pictorial record of that great Deluge of 



which the Hebrew and the Babylonian accounts agree so 

 strikingly. The Altar lies entirely below our English 

 horizon; the Wolf, the somewhat inappropriate animal 

 whom tho Centaur is offering up, shows but two or 

 three faint stars; and Theta Centauri, the star in the 

 Ccntaiu-'s head, is the only bright member of that 

 constellation visible to us. 



THE PROGRESSIVE SPECTRUM OF NOVA 



PERSEI BETWEEN FEBRUARY 22 AND 



NOVEMBER 28, 1901. 



By Rev. Waltku Sidorpjaves, s.j., f.k.a.s. 



The new star is already old while its birth and rapid 

 growth are fresh in our memories. Its brightness, its 

 colour, and its spectrum have been watched with 

 assiduous care throughout its short life, and a large 

 collection of spectrographic plates preserve the record 

 of sui-prising changes in the stmcture of its light beams, 

 for the study of tho futiu-e. The question now is. what 

 has been learned so far from this apparition iu Perseus? 

 Can it be, iu miniature, the life-history of a fixed 

 star, of unnumbered ages enacted in the brief span of a 

 few months .' Not, certiinly, in relation to its birth 

 and gi-owth; but iu its decline the Nova might have 

 been expected to exhibit tho stages of a star cooling. 

 The loss of heat, whether in ages or in months, should 

 pass through the same degi-ces of temperature; and the 

 successive spectra of Nova Pei-sei between Febiiiaiy 132- 

 23, when the star was at its greatest splendour, and 

 September 5, when it had fallen to near the seventh 

 magnitude, should liavo become the guiding signs for 

 tho classification of stai-s on the descending scale of 

 tempcratm-e. But the changes have been too rapid ; 

 the process of ages has been i-ushed through in houi-s 

 rather than in months ; and no one knows what has 

 been hidden from us in the day-light houre and by the 

 evening clouds of Febiniary 24. 



On Febi-uaiy 22 the spectrum of the star was found, 

 at Harvard College in America, to be of the Orion type, 

 with the first glimmer of bright radiation at the red 

 side edges of the hydrogen lines. On Februai-y 23, at 

 the same observatory, a faint photograph " showed no 

 marked change, except that the line K was present." * 

 On the same date at Edinburgh the visual spectiiun 

 was described as " a distinct but feebly developed solar 

 typo"; t and on the Potsdam plates the 9 hydrogen 

 lines, from Hfi to 11k api^eared as " broad absorption 

 bands, veiy weak, diffuse, and only recognisable with 

 difficulty. ' I 



On Febi-uai-y 24 a great change in the spectrum was 

 found on the photographs at Han'ard College, and at 

 the Yerkes Observatoiy. " It was traversed by numerous 

 bright and dai'k bands, and closely resembled that of 

 Nova AiU'igae." § 



Thus in the short space of 48 houre the star's 

 spectrum had changed from that of a white star of the 

 Orion typo to a composite spectrum of bright and dark 

 lines: a change to be worked out on a fixed star in 

 ages of time ! The intermediate changes are not so 



* Ap. J., XIII., 172. 

 I Vogel, Ap. J., 218. 



t Edinburgh Circular, Jfo. 5-i. 

 § Pickering, Ap. J., XIII., 172. 



