280 



SCIENCE. 



[N. S. Vol. III. No. C>n. 



published during the present year. The work 

 will embody the lectures delivered at Columbia 

 College by Dr. Hill, and will appear with the 

 imprint of the Columbia University Press. 



H. J. 



HAEVARD COLLEGE OBSERVATORY, CIRCULAR 

 NO 5. 

 Wells' Algol Variaile. 

 A MINIMUM of the Algol star, B. D. + 17° 

 4367, occurred, as predicted in Circular No. 4, 

 on the afternoon of January 5, 1896. Through 

 the courtesy of Professor Young, observations 

 were obtained at Princeton by Professor Taylor 

 Eeed, with the 23-inch equatorial. It was also 

 observed by Mr. W. M. Reed at Andover. 

 Preparations had been made at this observatory 

 to obtain a series of photographic images of it 

 automatically, each having an exposure of five 

 minutes to observe it photometrically with the 

 15-inch equatorial, and also visually with the 

 12 and 6-inch equatorials. Unfortunately, ow- 

 ing to clouds, few observations were obtained, 

 but these serve to show that the star was faint 

 and diminishing in brightness as expected. 

 Similar preparations were made for the next 

 minimum, January 10, but again clouds pre- 

 vented observation. 



The observations so far obtained show that 

 its time of minimum, uncorrected for the 

 velocity of light, can be closely represented by 

 the formula J. D. 2412002.500 + 4.8064 E. The 

 uncertainty in the period does not exceed a few 

 seconds, and will probably be known within a 

 single second as soon as the form of light curve 

 is determined. For nearly two hours before 

 and after the minimum it is fainter than the 

 twelfth magnitude. It is impossible, at present, 

 to say how much fainter it becomes or whether 

 it disappears entirely. It increases at first very 

 rapidly and then more slowly, attaining its full 

 brightness, magnitude 9.5, about five hours after 

 the minimum. One hundred and thirty photo- 

 graphs indicate that during the four days be- 

 tween the successive minima it does not vary 

 more than a few hundredths of a magnitude. 

 The variation may be explained by assuming 

 that the star revolves around a comparatively 

 dark body and is totally eclipsed by it for two 

 or three hours, the light at minimum, if any, 

 being entirely that of the dark body. The 



conditions resemble those of U Cephei, which 

 appears to be totally eclipsed by a relatively 

 dark body two and a-half magnitudes fainter 

 than itself, but having a diameter at least one 

 half greater. The variation in light of B. D. 

 + 17° 4367 is more rapid than that of any other 

 star hitherto discovered, and as its range is 

 greater than that of any known star of the 

 Algol type, its form of light curve can be de- 

 termined with corresponding accuracy. U 

 Cephei is second in both these respects. 



The New Star in Centaurus. 



In circular No. 4 insert ' it ' before ' follows ' 

 in the ninth line. This word was given cor- 

 rectly in the printer's cojoy, but was omitted in 

 setting the type. The correction was tele- 

 graphed to those astronomers who, it was ex- 

 pected, would use it. The Nova follows the 

 nebula N. G. C. 5253, and is north of it. The 

 nebula is assumed to be C. DM. —31° 10536, 

 magn. 9.5, with which it was originally identi- 

 fied. As seen with a low power the nebula can- 

 not readily be distinguished from a star. Its 

 magnitude on the Cordoba scale by comparison 

 with adjacent stars was estimated by Mr. Wen- 

 dell as 9.7, and it could hardly have been over- 

 looked in preparing the Cordoba Durchmuster- 

 ung, in which many adjacent fainter stars are 

 given. The new star could not have been ob- 

 served at Cordoba unless we assume, first, that 

 it was bright at that time, although invariably 

 too faint to be photographed on fifty nights dis- 

 tributed over six years, and secondly, that the 

 nebula was overlooked at Cordoba while ob- 

 serving fainter objects in the same region. 

 Even if we make these assumptions, the new 

 star still falls in the same class as T Coronae, 

 which was observed in the northern Durch- 

 musterung several years preceding its appear- 

 ance as a new star. 



The various positions of N. G. C. 5253 for 

 1875 are as follows: — 



Dreyer's New General Catalogue E. A. = 13" 32" 51' 



Dec. — —31° 0'.2 

 Cordoba Durchmusterung E. A. — 13" SS" 49'.6 



Dec. =:: —31° 0'.3 

 Plate B 13965 E. A. =13" 32°" 50^2 Dec. = 



— 31° 0'23" 

 Plate B 14072 E. A. = 13" 32°' 50».0 Dec. = 



—31° C 21" 



