492 



NATURE 



[August 22, 1918 



Faint Stars with Large Proper Motions. — Mr. 

 Furuhjelm's investigation of the proper motions of the 

 stars in the Helsingfors astrographic zone (39° to 

 46° N. decl.), between R.A. gh. and I2h., has already 

 been, noticed in Nature. He has now published a 

 smaller list [Ofversigt af Finska Vetenskaps-Societe- 

 tens Forhandlingar, Bd. lix., Afd. A., No. 22), which 

 extends from R.A. oh. to 24h., but includes only stars 

 the annual proper motion of which is 0-5" or more. Thev 

 are sixty-three in number, but the proper motions of 

 more than half of these had already been published. 

 However, more than twenty are new, being faint 

 stars of the loth'or nth photographic magnitude. 

 They have been derived by the aid of the blink micro- 

 scope from pairs of plates taken at intervals of several 

 years. The author believes that the list contains all 

 the stars in the zone down to the nth magnitude, 

 whose P.M. amounts to 0-5". In a separate publica- 

 tion he gives a detailed study of the faint star which 

 he found in 1914 to have the same P.M. as Capella. 

 His final result for its P.M. is 4-o-oo7is. in R.A., 

 — 0-434" i" decl., Boss's values for Capella being 

 +00082S., —0-429". The place of the small star (the 

 photographic magnitude of which is 10-6) for 1900-0 

 was 5h. lom. i-20s., +45° 44' 21-5", that of Capella 

 being 5h. 9m. 18-04S., +45° 53' 47-0". The distance 

 between them is 12' 4". Making allowance for the 

 greater distance of Capella from the sun, the system 

 shows a close analogy to that of oCentauri and its 

 distant companion, which Mr. Innes has named 

 Proxima. 



Periodicity of Solar Radiation. — In continuation 

 of the preliminary work of Clayton (Nature, vol. c, 

 p. 14), Dr. C. G. Abbot has made a further investiga- 

 tion of possible periodicities in the short-interval 

 variations of the "solar constant" (Smithsonian 

 Miscell. Collections, vol. Ixix., No. 6). The method 

 adopted was to calculate the coefficients of correla- 

 tion between the solar constants of given days and 

 those of one to forty days later, as observed from 

 1908 to 19 1 6. There appears to be no well-marked 

 periodicity which persists through the whole period of 

 observation, but some of the results for individual 

 years are of interest. Thus, in 1915, a period of about 

 twenty-seven days, doubtless associated with the solar 

 rotation, was strongly shown, the observations sug- 

 gesting that one side of the sun was hotter than the 

 other during several rotations. This result is of con- 

 siderable importance as furnishing additional evidence 

 that the short-period variations are of truly solar origin. 

 The year 1916 was unique in giving indications of a 

 period of about 3^ days. 



The Spectrum of Mira. — The bright lines re- 

 corded in the spectrum of Mira by Stebbins in 1903 

 have been further investigated by W. S. Adams and 

 A. H. Joy (Pub. Ast. Soc. Pac, vol. xxx., p. 193). 

 Some additional lines are shown in a photograph taken 

 on March 2, but the principal interest attaches to 

 the suggested Identifications of the lines. Apart from 

 the well-known lines of hydrogen, the bright lines 

 appear to be mainly due to iron and magnesium, and 

 in each case the lines involved are those which have 

 their greatest intensity at low temperatures. The 

 brightest line, next to the lines of hydrogen, is the 

 magnesium line A 4571, which is the most charac- 

 teristic line of the f!ame spectrum. Similarly, the 

 iron lines which occur are those of the low-temperature 

 groups a and h of the classification of Gale and Adams. 

 The lines in question make their appearance, or at 

 least become more intense, as the star approaches its 

 minimum of light, and it would seem that the radia- 

 ting gases undergo a reduction of temperature as the 

 star becomes fainter. 



NO. 2547, VOL. lOl] 



THE NEW STAR IN AQUILA. 

 HE following estimates of brightness of Nova 

 Aquilae rnade by M. Paul Blanc at Fourcalquier 



are included in Circular No. 2 

 Observatory : — 



of the Marseilles 



Details are also given of determinations of the 

 brightness of the nova in the wave-lengths 645, 558, 

 and 412 made at Florence by M. Maggini. The 

 observations indicate that the nova did not radiate 

 as a black body. 



The following collection of references to the history 

 of the nova prior to the outburst in June has been 

 communicated by Dr. C. Easton, of Amsterdam : — 

 1892, August 14, Algiers Astrogr. Chart No. 341 

 (Zwiers), mag. 8-8; 1894, September 21, Barnard's 

 Photographs of the Milky Way, Publ. of Lick Obs., 

 vol. xi., plate 59 (Easton), mag. 10-5; 1895, June 26, 

 Algiers- No. 141 (Jonckheere), mag. 8-8; id., 1909, 

 August 20, mag. <8-8 {vide Nature, No. 2537);. 

 1909, June 20, M. Wolf, Ast. Nach., No. 4949,- 

 mag. 10-5; 1910, Franklin Adams Chart, mag. 1 

 <8-8,' 1912, July, Bailey's N. Milkv Way, Harvard' 

 Annals, vol. Ixxx., No.' 4 (Nijland). In' Barnard's; 

 photograph of 1894 the nova is 20 mm. from the left, ; 

 and 5-5 mm. from the bottom of the plate. Dr. 

 Easton remarks that there seems to be sufficient evi- 

 dence of the variability- of the nova. 



Messrs. I. Yamamoto and Y. Ueta, of the Kyoto 

 University, inform us that they independently dis- 

 covered the new star on June 11, during an expedition 

 to observe the recent total eclipse of the sun. Owing 

 to the rainy season very few observations were secured, 

 but it was observed that the star became fainter and 

 redder until June 29, when there was a slight recovery. 



The star is still easily visible to the naked eye, 

 being now between the 4th and 5th magnitudes. On 

 August 10 Prof. Fowler noted that the green nebular 

 line was the most conspicuous feature of the visible 

 spectrum. 



Father Cortie sends the following records of 

 observations on August 13 and 15. On the former 

 date the star, according to Mr. Butterworth, was 

 of magnitude 4-3 visually and 4-7 photographically. 

 The maximum of brilliancy has shifted from the red 

 to the green, and the image in the telescope has lost 

 its ruddy hue, and is of a blue tint. In a McClean 

 spectroscope H^ was very much reduced in brightness ;, 

 a yellow line, presumably D, was seen, and vivid 

 brio-ht lines at 5007. H^, 4640, and about H^. The 

 following wave-lengths of the principal bright bands 

 wfere determined from a photograph : 3867, Hf, H„ 

 H«, H^, 436?, 4640, 4680, 4713, H/3, 4958. and 5007. 

 The bands about H.^ and 4640 were the brightest. On 

 August 15 H^ and 4363 were the brightest. The mean 

 width of the hydrogen bands is about 50 Angstrom 

 units. While the bands at H^ and 4640 are triple in 

 character, Hs is composed of a double band. The 

 spectrum on the dates named was almost exactly like 

 that of Nova Persei in August and September, 1901, 

 when its magnitude was between 6 and 7. 



