ASTRONOMICAL PROGRESS IN 1899. 



55 



have been numbered, and a few have been named 

 as indicated: 



DT 436, discovered by Wolf. 

 DU438, discovered by Charlois, Nov. 8, 1898. 

 EB 439, discovered by Coddington, Oct. 14, 1898. 

 EC 440, discovered by Coddington, Oct. 14, 18*J8. 

 ED 441. discovered by Charlois, Dec. 9, 1898. 

 EE 4452, discovered by Wolf, Feb. 15, 1899. 

 EF 443, discovered by Wolf, Feb. 17, 1899. 

 EL 444, discovered by Coggia, March 31, 1899. 



Nearly a dozen others were found and received 

 provisional letters, but they proved to be those 

 discovered several years ago. The following as- 

 teroids have received names: No. 420, Bertholda; 

 No. 421, Ziihringia; No. 422, Berdina; No. 428, 

 Monathia; No. 433, Eros; No. 439, Ohio. 



An asteroid discovered six years ago, No. 366, 

 which has had only a provisional number, has 

 lately been named Vincentina. 



Asteroid 433 (DQ), about which so much in- 

 terest is taken on account of its anomalous or- 

 bit and the value it will have for astronomy, has 

 been named Eros. A brief notice of its discovery 

 was given in the last volume of the Annual 

 Cyclopaedia, before the great value of the discov- 

 ery was fully appreciated or its orbit accurately 

 computed. -The number of asteroids now known 

 is about 450, all between the orbits of Mars and 

 Jupiter except the one under discussion. The 

 labor of keeping track of so many is great, and 

 the announcement of the discovery of another is 

 treated with indifference bordering on disgust; 

 but the discovery of Eros has opened a broad 

 field for speculation, as it may be the forerunner 

 of others moving in the same or similar orbits. 

 It was discovered by photography; its trail, a 

 long one, was found on the plate with two short 

 ones, which immediately indicated that if it was 

 not that of a comet then there must be an as- 

 teroid with an orbit unlike any of the others. 

 A few observations showed that two thirds of 

 its orbit lies between the orbits of the Earth and 

 Mars, instead of between Mars and Jupiter. At 

 certain times it can approach nearer the Earth 

 than any heavenly body except the Moon, and be 

 just visible to the naked eye. It makes one of 

 these nearest approaches only once in about 

 thirty-one years, when its parallax will amount 

 to almost a minute; and of all the means that 

 can be used for the ascertainment of the Sun's 

 distance from the Earth, including the transits 

 of Venus, this little insignificant world is worth 

 the most. We have always considered Mars as 

 our nearest outside and Venus the nearest inside 

 neighbor, but now it is Eros and Venus. At its 

 least distance from the Earth Eros is only 0.15, 

 in terms of the Earth's distance from the Sun, 

 as compared with 0.27 for Venus in transit, 

 equal to 25,650,000 raises, and 0.38 for Mars in 

 perihelion, equal to 35,300,000 miles, or only 

 14,000,000 for Eros. 



The Earth passes the longitude of the asteroid's 

 perihelion (nearest the Sun) on Jan. 22, and in 

 order that the Earth and the asteroid be nearest 

 together the asteroid must pass perihelion on 

 or near that date, which it will not do till 1931. 

 But, fortunately, quite a near approach will take 

 place in December, 1900, the distance being 0.33, 

 at which the little planet will be between the 

 eighth and ninth magnitude. When discovered 

 it was of the eleventh magnitude, and three and a 

 half years previous it must have been of the sixth 

 and a half. The diameter of the little world is 

 about 17 miles. 



If its parallax can be obtained, Kepler's third 

 law gives at once the distance of the Earth from 

 the Sun, whinh is the " yardstick " that " de- 

 termines the distances of all the planets from the 



Sun and from each other, and their diameters and 

 orbital velocities." Prof. Pickering found the 

 trail of Eros on 13 plates exposed during l893-'96, 

 the photo-magnitudes varying from 8.2 to 12.5. 

 During the search for Eros on the plates Mrs. 

 Fleming found images of two variable stars, one 

 of which fails to appear on 10 plates. All the 

 photographs on which Eros was found were 

 taken with doublets. Had lenses of the usual 

 form been used, with a field only 2 degrees in 

 diameter, all the images of Eros would have fallen 

 outside the plates. 



Dr. S. C. Chandler, editor of the Astronomical 

 Journal, has computed the following elements of 

 Eros, using recent observations combined with 

 positions found on Harvard plates in 1894: 



EPOCH 1898, AUG. 31.5, GREENWICH MEAN TIME. 



Mean anomaly 221 35' 45.6" } 



Node to perihelion 177 37' 56.0" 1ono n 



Longitude of node 303 31' 57.1" f 



Inclination of orbit 10 50' 11.8" J 



Angle of eccentricity... 12 52' 9.8" 



Daily motion 2015.2326" 



Logarithm of mean distance 0. 1637876 



Period of revolution 643 . 10 days 



Saturn's Ninth Satellite. Attempts have 

 been made to discover new satellites to the plan- 

 ets by photography, but they have failed, from 

 the low rapidity of the lenses employed. On 

 Aug. 16, 17, 18, 1898, four plates were exposed 

 for two hours each, with the lens presented to 

 Harvard College Observatory by Miss Catharine 

 Bruce, of New York, which has 24-inch aperture 

 and only 13 feet 4 inches focal length. One 

 hundred thousand stars appeared on each plate. 

 The photographs were examined two at a time, 

 one superimposed on the other, and placed film 

 to film, so that each star was represented by two 

 contiguous dots, the satellite showing itself by 

 a single dot, sharing in the motion of Saturn rela- 

 tively to the stars. The position of the satellite 

 is nearly the same on the two plates taken on 

 Aug. 16. On Aug. 17 it followed this position 

 35" of arc, and was south 19". On Aug. 18 it 

 followed 72", and south 43". Its motion was di- 

 rect, but slower than that of Saturn, and nearly 

 in the same direction. It therefore can not be 

 an asteroid, but must be either a ninth satellite 

 to Saturn or an ultra-Neptunian planet. Prof. 

 Pickering, who has thoroughly investigated all 

 the circumstances of this strange and unexpected 

 discovery, thinks the latter supposition exceed- 

 ingly improbable. It was at first identified with 

 a faint object found on the plates taken in 1897, 

 and the period of revolution around Saturn 

 (seventeen months) was thence derived; but this 

 is not confirmed, and the period is now in doubt. 

 The position angle in May, 1899, was between 

 280 and 290, and the distance between 20 

 and 30 minutes. The uncertainties will prob- 

 ably be diminished when plates taken at the 

 Harvard Observatory station at Arequipa, Peru, 

 on Sept. 15, 16, and 17, 1898, are received at 

 Harvard College Observatory. The apparent or- 

 bit of the supposed satellite is a very elongated 

 ellipse. From comparisons with Hyperion, the 

 faintest of his satellites, the magnitude of the 

 new one is estimated at 15.5. As seen from Sat- 

 urn, it would appear of the sixth magnitude, 

 or as faint as the faintest star visible to the 

 naked eye. If its reflecting power is the same 

 as his largest satellite, Titan, its diameter is esti- 

 mated to be only about 200 miles. Prof. William 

 H. Pickering, its discoverer, suggests the name 

 Phoebe, sister of Saturn. It thus appears that . 

 this unique planet is adorned with 9 moons, en^ 

 vironed in 3 rings, and sometimes 5. 



