ASTRONOMICAL PROGRESS IN 1902. 



PROVISIONAL. 



PROVISIONAL. 

 LtUcn Humbert. Namei. 



GB. 



GJ 470 = Kilia. 



GN 471 



GP 472 = Roma. 



GC 473 



GD 474 



HN 475 = Ocllo. 



GO 476 = Hedwig. 



GR 4~ 



478 



HJ 



No. 448, Natalia, was discovered by the late 

 Prof. Keeler in 18SM). with a 3-foot reflector. It 

 is the faintest of all the family, and is of the 

 twentieth magnitude. 



Nearly 30 others have provisional letters as- 

 -i.-iH'd to them, some of which, no doubt, will be 

 found to be identical with some previously dis- 

 covered. A few have been seen but once, so pro- 

 visional numbers were withheld until further 

 investigation. It is safe to assume that 500 of 

 these little worlds have been discovered. The 

 most distant of the minor planets is 279 Thule. 

 The nearest is 433, Eros, which occasionally ap- 

 proaches nearer the Earth than any heavenly 

 body except the Moon. 



N'O. 475, Ocllo, has a southern declination of 

 61i. Its daily orbital motion amounts to the 

 enormous sum of 2,200", or did when in perihe- 

 lion, and it is the nearest to the Sun of any of 

 the family except Eros. It was found depicted 

 on a photographic plate by Steward, at the Har- 

 vard College Observatory station at Arequipa, 

 Peru. 



Variable Stars. The search for stars that 

 vary in brightness is to most astronomers a 

 pleasing pastime. The high interest attaching to 

 their discovery and subsequent investigation into 

 their periods and fluctuations in brightness have 

 led many astronomers to devote their lives to the 

 fascinating work. The number discovered since 

 last report is so great and varied that amateurs 

 have taken up the subject, as no expensive in- 

 struments are needed, and are assisting the as- 

 tronomers in their further discovery and inves- 

 tigation. 



Many explanatory theories have been ad- 

 vanced to account for their variation. There are 

 three varieties: 1. Those that vary equally 

 (though different for different stars) from maxi- 

 mum to minimum, and vice versa, varying as 

 regularly as the changes of the Moon. This va- 

 riety is called Algol variables. 2. Those that 

 vary intermittently or fitfully without any re- 

 gard to periodicity, sometimes to invisibility. 3. 

 Temporary stars, which burst out in an instant, 

 surpassing even Jupiter in brilliance, as did the 

 recent outburst in Perseus, the brightest since 

 the notable one of 1572. 



Algol variables are reasonably accounted for by 

 supposing they are periodically occulted by an 

 opaque object, which partially eclipses them, 

 and this accounts for all that is observed by the 

 telescope and spectroscope. 



The hypothesis meets with general acceptance 

 among astronomers. 



To explain the cause of the fitful variables and 

 the sudden outbursts of the temporaries no the- 

 ory worth recording has been promulgated. 



The number of variables now known is more 

 than 2.5(10, and further discoveries are being made 

 at a rapid rate. One astronomer asserts that one 

 star out of every five is a variable. The state- 

 ment scorns extravagant, but he doubtless in- 

 cluded the minute spectroscopic variation of 

 many, caused by their slight motion to and from 

 the earth in the line of sight. In their discovery 



and the investigation into the cause of their 

 variation photography is doing good work, of 

 which the following is one example among hun- 

 dreds: Prof. E. C. Pickering, describing the dis- 

 covery of a remarkable variable star, says, in 

 Circular No. 65, it was found that a photograph 

 on glass of the region in which Brooks's comet 

 was discovered on April 14, 1902, had been taken 

 at the Harvard Observatory on April 3. This 

 was superposed on another taken on March 7, 



1900, resulting in the discovery of a new variable 

 of the Algol type in R. A. 21 h 55.2 m , declination 

 north 43 52'. The true period of the new variable 

 is about 31.304 days. It retains its full brightness 

 for twenty-eight days, its photographic magni- 

 tude at maximum being 8.9. About a day before 

 minimum it begins to diminish, attaining the 

 magnitude 9.0 at 1.05 d before minimum, 9.5 at 

 0.94 d , 10.0 magnitude at 0.84*, 10.5 at 0.71 d , 11.0 

 at 0.58 d , and 11.5 at 0.43 d . The time of increase 

 is apparently the same as that of decrease. The 

 light remains nearly constant for more than half 

 a day, with the minimum magnitude 11.6. The 

 period of the variable is more than three times 

 that of any other yet discovered, and the dura- 

 tion of minimum (two days) is double that of 

 S Cancri, the next in length. These results have 

 been obtained from an examination of 388 plates, 

 taken between 1888 and 1902. 



Prof. Robert Innis, in his revision of the Cape 

 catalogue, discovered 4 new variables, all, in 

 one respect at least, very interesting. One desig- 

 nated 29, 1900, Appodis, varies from 8.0 magni- 

 tude to invisibility. Its period has not been as- 

 certained, but the periods of the other three are 

 from three hundred and sixty to four hundred 

 days, and they diminish in brilliance to invisibil- 

 ity, suffering periodically a total eclipse. 



Dr. Anderson, who makes the discovery of vari- 

 ables a special line of work, calls another new 

 one 77, 1901, Herculis. Soon afterward A. Stanley 

 Williams discovered one with the designation 78, 



1901, Cygni. It is of the Algol type. Its normal 

 brightness is tenth magnitude, but after 3 d 2 h it 

 diminishes to the twelfth, at which it remains for 

 fifty minutes. In 4 h 10 m it recovers its usual 

 brightness. 



Harvard College Observatory Circular No. 54 

 gives a list of 64 new variables, the greater part 

 being southern stars discovered by the presence 

 of bright hydrogen lines in their photographed 

 spectra. 



Mira Ceti is considered the most remarkable of 

 all the variables. It was discovered to be a vari- 

 able star more than three hundred years ago. 

 Y\ 'hen at its maximum brightness it shines as a 

 second-magnitude star, but it dwindles down to 

 the 9J magnitude. Recent investigation shows 

 that it is not an Algol star. In the little globu- 

 lar cluster surrounding Omega Centauri 125 va- 

 riables are visible, Omega itself being one of them, 

 with a period of only six hours and twelve min- 

 utes. Another remarkable variable is Eta Argus, 

 often invisible to the naked eye, but in 1838 and 

 1843 it surpassed in brightness every star in the 

 sky except Sirius. The shortest known variable 

 is U Pegasi = 4h 29>n 8", the longest is R Cari- 

 nae = thirty-seven or thirty-eight years. 



Stellar Photography. Prof. E. C. Pickering 

 has for many years been taking celestial photo- 

 graphs. He has a library of glass, so to speak, 

 of more than 30,000 plates, all numbered, dated, 

 their right ascensions, and declinations recorded, 

 packed away in the order of right ascension, so 

 that a plate of any locality in the sky can be 

 found in a moment. In his fifty-sixth annual re- 

 port for 1901 is the statement that the number of 



