50 



ASTRONOMICAL PROGRESS IN 1896. 



Observatory at Pulkowa, Russia, whose observations 

 tend to show that in addition to the two visible com- 

 ponents of Castor (Alpha 1 and Alpha 2 , Geminorum) 

 Alpha 1 must have a dark companion akin to that 

 of Algol (Beta Persei), save that, while the latter is 

 periodically occulted by its companion, no such 

 phenomenon happens in the case of Alpha 1 Gemi- 

 norum. Photo-spectrographic observations indicate 

 that the effect of the companion is to change the 

 velocity of the star's motion at regular intervals in 

 the line of sight rather than to vary its brilliancy 

 by eclipse. Dr. Belopolsky concludes that the rela- 

 tive orbital velocity of the system is about 21 miles 

 a second. 



Prof. Bailey, of the Harvard College Observatory 

 at Arequipa, Peru, finds that Mu 1 Scorpii, like Beta 

 Auriga, Zeta Ursa Majoris, and others, is a spectro- 

 scopic binary. Its period of revolution is thirty-five 

 hours the shortest known. 



Spectrum of Alpha Aqnilae. In a memoir 

 presented to the Paris Academy of Sciences, M. 

 Deslandres makes the interesting statement that in 

 the spectrum of Alpha Aquike he has often seen 

 fine, double, bright lines running through the 

 middle of the dark lines of hydrogen, and some- 

 times even through those of iron and the K line of 

 calcium. He attributes them to the star's chromo- 

 sphere, and regards them as proof of the orbital 

 motion of the star, and also of an atmosphere sur- 

 rounding it, as in the case of our Sun. 



Rediscovery of the Companion to Sirius. 

 This difficult object, which, owing both to its mi- 

 nuteness and to the overpowering brilliance of the 

 primary, has been invisible for a few years during 

 its periastron, was refound at Lowell Observatory, 

 Flagstaff, Arizona, on Aug. 31, by Dr. See. ' Angle 

 of position, 219 ; distance, 5-9'. This companion 

 star was originally discovered, visually, by Alvan 

 G. Clark, of Cambridge, Mass. 



Photographing the Nebulae and Clusters. 

 This work is still zealously carried on by Isaac Rob- 

 erts at his observatory in Sussex, England. In 

 " Monthly Notices," Vol. LVI, No. 5, is a list of 82 

 of these objects, with exposures of from three min- 

 utes to four hours, which revealed conditions in 

 each not visible in any telescope. Among these is 

 the new star in Auriga, to which he gave an expo- 

 sure of three hours, with the result that it confirms 

 the suspicion of Dr. Barnard that it is no longer a 

 star but a nebula. 



During the year much time was spent in deter- 

 mining the relative efficiency of his 20-inch reflector 

 in the delineation of celestial objects as compared 

 with portrait lenses, and his conclusions are pub- 

 lished in " Monthly Notices," Vol. LVI, No. 7. He 

 decides that the reflector form is much superior to 

 'that of the refractor portrait lens. His experiments 

 point also to a practical limit of aperture to focus 

 in the construction of instruments for celestial pho- 

 tography, which limit he deems not far from 1 to 5. 

 He finds a deterioration in the stellar images if the 

 ratio be 1 to 4, and if it be 1 to 6 the photographic 

 effect is slower and, consequently, inadmissible. 

 One trial was made close to Gamma Cassiopeia with 

 4 telescopes : First, 3|-inch portrait lens : aperture 

 to focus, 2'74; exposure one hundred and thirty- 

 two minutes ; and on 2 x 2 1,680 stars were counted. 

 The two nebula? were visible, but without structural 

 details. In the second experiment a 5-inch portrait 

 lens was used ; focus. 4'8 ; exposure one hundred 

 and thirty-two minutes; giving 2,610 stars on 

 2 x 2 . Nebula well shown, and some of the in- 

 volved stars. In the third, by Barnard, a 6-inch 

 Willard lens was used ; focus, 5'4 ; exposure one 

 hundred and eighty minutes ; result, 1,300 stars on 

 2' x 2 r '. The two nebulje were present, and some of 

 the involved stars, but with less density and clear- 



ness than with the 5-inch. In the fourth experi- 

 ment a 20-inch reflector was used ; focus, 4'9 : ex- 

 posure one hundred and thirty-two minutes; 17,100 

 stars on 2" J x2'. Nebula 1 brilliantly shown with 

 many stars, both bright and faint, involved in the 

 nebulosity. The importance of these studies war- 

 rants the mention of two other trials in the cluster 

 of the Pleiades: First, with a Willard lens ; expo- 

 sure four hours ; shows Merope nebula, but without 

 structural particulars, also a part of the Elect ra 

 nebula, but all the rest of the nebulosity in the 

 cluster is lost by the large halation circles sur- 

 rounding the bright stars. On 2 x 2 825 stars are 

 visible, against 953 on the 5-inch-lens plate and 

 3,470 stars on the reflector plate. The exposure 

 of the last two being two hours fifty minutes, 

 against four hours with the Willard ' lens. Mr. 

 Roberts thinks these facts tend to raise doubt as to 

 the existence of the large nebular field outside the 

 Pleiades, depicted on some of Dr. Barnard's plates. 

 While, no doubt, much is yet to be learned regard- 

 ing the best form of instrument for celestial pho- 

 tography, yet the light-grasping power of the 6-inch 

 Willard lens used by Dr. Barnard is very small 

 compared with the 20 inch reflector, which latter, 

 to have given only an equal amount of light, 

 should have been contracted to about 7 inches. 



Photographing the Nebula near \i Persei. 

 This nebula was discovered by Barnard in 1885, 

 and is No. 1499 of the New General Catalogue. An 

 enlarged photograph of this remarkable nebula and 

 the surrounding sky was shown in the " Astro- 

 physical Journal " for December, 1895. An expo- 

 sure of six hours was given to the negative plate. 

 The nebula is large and very elongated, its extreme 

 length being 1'2. Though it is not resolved, yet 

 many stars are shown in it, and many thousands 

 surrounding it. It shows many condensations of 

 light and one dark spot, evidently a hole through it. 



The Pleiades. The astronomer at Tashkend, 

 M. Stratonoff, announces three photographs of the 

 Pleiades, each plate having a long exposure, viz. : 

 No. 1, 9 h 45 m on three nights ; No. 2, twenty-five 

 hours on nine nights; and No. 3, 17 h 30 on nine 

 nights. These were taken with the great Repsold- 

 Henry refractor, which since 1894 has been the 

 possession of the observatory at Tashkend. Of 

 the three pictures, the third is the most interesting. 

 In 4 square degrees, 2x2, the Pleiades in the 

 center, 6,614 stars are depicted, with many fresh 

 details of those already known, as well as several 

 nebuht unseen before. One of these has the form 

 of a right-line streak and is nearly parallel to the 

 similar nebula discovered by Henry. Another is 

 made up of streaks crossing each other in various 

 directions. 



The Photographic Chart of the Sky. This 

 gigantic and unprecedented astronomical task 

 nears completion, and to decide on the final ar- 

 rangements for its close was the object of the In- 

 ternational Photographic Congress lately convened 

 in Paris. The plan outlined, which lias been fol- 

 lowed, was to photograph every star in the heavens 

 down to the fourteenth magnitude (nearly 50,000,- 

 000 stars) with mathematical exactness bot'i as to 

 magnitude and position. The work was divided 

 among eighteen European observatories, each with 

 its section of the heavens, from which it has secured 

 3,000 photographs. Unfortunately, no observatory 

 in the United States felt that it could give the ne- 

 cessary time to this work. Of the stars, at least 

 2,500,000, including those from magnitudes 1 to 

 11, will be catalogued and numbered. The com- 

 plete map will consist of 27,000 parts, and, if 

 spread out and adjoined, will cover an area of 

 nearly two acres. Its cost has been $2,000.000. For 

 the covering of the entire heavens 11,027 plates, 



