ASTRONOMICAL PROGRESS IN 1902. 



39 



Dr. Hartmann, in a Berlin astronomical pub- 

 lication of Feb. 27, 1902, describes experiments 

 made with the Potsdam photographic refractor, 

 with two different spectroscopes, one having a 

 flint-glass prism of 00 and '3 of 63. The ex- 

 posures were from 90n to 270 m . The velocity 

 of the nebula, General Catalogue, 4390, was first 

 determined from measurements of the line Hj8 

 and Hy, which were very satisfactory. Their 

 motions in the line of sight were: 



G. C. 4390 = - 10.5 kilometers a second. 



" 4373= -63. 8 

 New " 7027= + 4.9 " " 



The great nebula in Orion has been subjected 

 to a similar spectrogramic analysis, and the result 

 indicates a motion in the line of sight by using 

 the H/8 line, amounting to + 6, + 41, and + 28 

 kilometers a second. The results of measures 

 made by three experts are, as might be expected, 

 somewhat discordant, because of the faintness of 

 the lines. 



Double Stars. During the past one hundred 

 years the search for double stars, the investiga- 

 tion of their motions, and determinations of their 

 period if binaries have constituted an important 

 division of sidereal research. In the past thirty 

 years 4,000 double stars have been discovered, all 

 by a few astronomers. In 1902 several hundred 

 new ones were found. Nearly 12,000 double stars 

 are now known. 



If two stars are found by the telescope to be 

 excessively close to each other, in which after 

 several years no motion of revolution is observed, 

 the pair is called an optically double one. If mo- 

 tion of revolution is detected, it is called a binary. 

 A few trinary systems are known, of which the 

 pole-star is an example. Prof. Hussey, of the 

 Lick Observatory, has discovered that Burnham's 

 double star 168 is a trinary, one component being 

 an exceedingly close double, the distance being 

 less than 0.4". The companion is a spectroscopic 

 double which yields to no telescope. The tele- 

 scope sees two, the spectroscope deals with three. 

 The following short list includes a few of the 

 most interesting telescopic binaries, of which 

 about 400 are known: 



Period of Rotation. 



5 . 5 years. Shortest known. 

 114 

 W 



16 

 40 



Name. 



Burnham 883 



Kappa Pegasi 



Delta Equelei 



82 Ceti 



Zeta Herculis 



Procyon 40 



Sirius. doer-star 58 . 8 



Xi Ursse Majoris 61 



Alpha Centauri 81 



x 70Ophiuchi 94 



Gamma Virginis 200 



Gamma Leonis 400 



Castor 1,000 



Zeta Aquarius 1,500 



The vast difference between the periods of the 

 first and last will not escape notice. To separate 

 many of the double stars eyepieces magnifying 

 from 1,000 to 5.000 diameters are used. Prof. 

 Hussey, examining some well-known double 

 stars, found 5 of them triple, 4 as close as 0.6", 

 and one only 0.3", the closest telescopic binaries 

 yet discovered. 



A large variation is shown in motion in line 

 of sight of Omicron Persei. Its range of varia- 

 tion and that of Eta Orionis are the largest yet 

 discovered among spectroscopic binaries that 

 have a dark component. The well-known Algol 

 variable Delta Librae also exhibits considerable 

 variation in radial velocity. Ten spectrographs 

 of Sirius were obtained between December, 1901, 

 and March, 1902, which give for the epoch 



1902.06 a velocity in line of sight of 6.87 kilo- 

 meters a second. This result, combined with 

 that obtained by Vogel and Scheiner, 15.6, for 

 the epoch of 1890.09, gives a parallax of 0.21" for 

 the system. Gill's value from heliometer meas- 

 ures is 0.37". The following are moving the most 

 rapidly : 



TOWARD THE EARTH. 



Milw In a 

 NMM - second. 



Arcturus 55 



Alpha Lyras 40 



Alpha Cygni 50 



Beta Gemini 60 



Alpha Ursae Majoris ... 60 



FROM THE EARTH. 



Nam.. *"" 



ecoud. 



Dog-star 20 



Castor 25 



Alpha Orionis 15 



Beta Orionis 22 



Gamma Leonis 25 



Comets. There was a dearth of comets in 

 1902, contrasting strangely with the number (10) 

 seen a few years ago. Comet (a) was discovered 

 by Prof. Brooks at Smith Observatory, Geneva, 

 N. Y., April 14, in the constellation Pegasus, 

 and in the same telescopic field as was that of 

 Feb. 23, 1883, also discovered by him. The direc- 

 tion and rate of motion were such that it was 

 constantly in the Sun's twilight. The few ob- 

 servations made indicated that it was moving in 

 a parabolic orbit, and therefore visited us for the 

 first and last time. Comet (6) was discovered on 

 July 22 by John Grigg, of New Zealand, but, from 

 places too roughly given and long delay by mail, 

 it was not seen elsewhere. Comet (c) was discov- 

 ered by Prof. C. D. Perrine at the Lick Observa- 

 tory on Sept. 1. It was very faint, about 4' in 

 diameter with a tail 30' in length. Its discovery 

 place was right ascension 3 h 17 m 49 s , declination 

 north 34 38' 47", or in the constellation Per- 

 seus. 



A finding ephemeris of Swift's comet 1895 II 

 is published, and astronomers are searching for 

 it by both photography and telescope, with but 

 little prospect of success, its position relative to 

 the Sun and Earth bemg unfavorable for visibil- 

 ity. It occasionally makes the nearest approach 

 to Jupiter of any of the periodics. When 

 this event next occurs its orbit will be greatly 

 changed, perhaps tq a very long period, or even 

 to a parabola. Mr. Schulhof estimates the un- 

 certainty of the time of perihelion passage at 

 only three days. 



Among the comets that have returned to peri- 

 helion unobserved is Finlay's of 1886, an espe- 

 cially interesting one from its supposed connec- 

 tion with Loxell's comet. E. Swift's comet, hav- 

 ing a period of 5.855 years, has also returned 

 without detection, much to the disappointment 

 of astronomers, as there is some reason for sup- 

 posing it to be identical with Di Vice's lost 

 comet. One of Barnard's comets is also in the 

 same category, having escaped detection at two 

 apparitions. 



Minor Planets. The search for these bodies 

 (called also asteroids and planetoids) is still 

 prosecuted with vigor, resulting as heretofore in 

 their rapid discovery, but more especially since 

 the employment of photography. It is supposed 

 that nearly all as bright as the tenth magnitude 

 have been discovered. Their diameters in miles 

 vary through wide limits. The mean diameter 

 of the four largest Ceres, Pallas, Juno, and 

 Vesta according to Prof. Barnard, is 285 miles. 



Ceres is the largest of the whole family, 477 

 miles. The smallest yet measured is No. 433, the 

 celebrated Eros, 15 to 20 miles. 



Minor planets are not searched for all over 

 the sky, as are comets, but at certain declinations 

 both north and south of the equator. The fol- 

 lowing have been discovered since the last re- 

 port : 



