6S 



KNOWLEDGE. 



February, 1911. 



VARIABLE OR NOVA LACEKTAE (ESPIM.— The 

 beginning and end of the year I'ilO were characterized by 

 important astronmnical discov.-ries ; the beginning was by the 

 Daylight comet, the end b\' a bright New star, which is 

 appropriate at this particular season of Epiphany. 



" Kiel 6.55 p.m.. received a! Oxford 7.33 p.m., December 

 31st, 1910. 



" To University Obs._r\ator:.-. Oxford. 



" Nova Lacertae Kspin Tow Law 30080 December 07359 

 Greenwich 33802 03744 72239 47224 Helle Linien." 



Thus runs the telesiMtn received by the subscribers to the 

 Central Office for .Astionomical Telegrams conducted by Dr. 

 Kobold at Kiel. Its meaning is that the Rev. T. E. Espin. 

 M..A., F.R.A..S.. lornierly of Exeter College, Oxford, and now 

 the Rector at Wolsingham. Tow Law. near Darlington, by 

 assiduousiv warching the sky and examining the stars for 

 duplicity and variability, was able to detect the appearance 

 of a b::tjiit star of about the seventh magnitude near the 

 edge o; the constellation Lacerta, towards Cepheus, at R.A. 

 22" iZ'° 10" 15' 21"+52= (1911). and in the Milkv Way. 

 about 6 p.m., on December 30th. Reference to maps failed to 

 show any star in that position, and upon examination with a 

 -pectroscope, bright lines were noticed in such positions as 

 indicated the star to be a new one, or one variable in 

 magnitude. The evening of December 31st was very cloudy. 

 At Oxford, on January 1st, two photographs of the region were 

 taken with four exposures of a few minutes each, and the 

 results of the measurement of one of these plates 

 were communicated to the Royal Astronomical Society's 

 meeting on January 13th, and will be published in the Monthly 

 Xoticcs in February. Photometric and eye estimations of its 

 magnitude have been made by Mr. Espin. and at the 

 observatories at Greenwich, Cambridge, Oxford (both obser- 

 vatories). Harvard College (U.S.A.) ; the magnitude was made 

 out to be between 7'0 and 8'0, or one-and-a-half magnitudes 

 brighter than the star near it. Various observers have noted 

 it as "red"; the writer has not yet been able to make it 

 deeper than " orange." and to him it appears to have 

 nothing of the " Hind"s crimson," R. or S. Cephei hue about it. 

 The magnitudes deduced from photographic plates, however, 

 do not fit in with the general ideas of chemical action, 

 colour, and photographic results ; for, if the colour be 

 red or orange and less actinic to the sensitive film of a mono- 

 chromatic plate (with emulsion such as is generally in use for 

 hand-camera and extra-rapid work), one would expect to get a 

 smaller image of it on the photograph than of a normal star, 

 both being determined by photometric or visual observation to 

 be of the same magnitude, say se\en. But the photographs 

 appear to give the magnitude on January 1st and 2nd as 6'7 

 or 6'6, or about two-thirds of a magnitude brighter than by 

 other methods. During the first part of January the star 

 changed or lost little, if any, of its brightness, 



Mr. F. \V. Dyson, the Astronomer-Royal, has received 

 information from the Harvard College Observatory that 

 the new star was visible on photographs exposed there 

 on November 23rd, 1910, when its magnitude was determined 

 to be equal to 9 Lacertae, or 5'0 photographically, and, there- 

 fore, quite visible without optical aid. The interesting feature 

 in the examination of the Harvard store of photographs, going 

 back many years, is that, on November 19th the star was not 

 visible, i.e., it was probably fainter than the eleventh 

 magnitude, if at all visible in the sky ; it was again photo- 

 graphed on December 7th, but, in spite of the large number 

 of telescopes, photographs, and keen observers searching the 

 sky, this naked-eye star was not detected until December 30th, 

 by Mr. Espin. 



Though some are disposed to consider the discovery to be 

 merely that of a variable, because rumours have been current 

 that Dr. Max Wolf has photographs, taken nearly twenty 

 years ago, which show a faint star in the position of the Nova. 

 — but we must wait for accurate measures, before accepting 

 this information — there is plenty of evidence for us to 

 consider it to be as much a new star as others. The immense 

 and nominally instantaneous brightening up by eight, ten, or 

 more magnitudes — as in the most prominent cases of 



T. Coronae (1868), Nova .Andromedae (1885), Nova .Aurigae 

 (1S92), Nova Persei (1901), and Nova Geminorum (19031 — 

 classify these Novae as being of a different order from all 

 known \ariable stars, though their spectra may be similar. 



Two questions arise and present themselves for astronomers 

 to solve, now that thousands of photographs, taken during the last 

 thirty years, are available for reference. When is a Xova not 

 a Xova ? And who is to be entitled to the credit of the 

 discovery in such cases as Nova Geminorum and the star 

 which is the subject of this note ? Surely not the one who 

 first saw or photographed it. but the one who first drew the 

 attention of the astronomical world to it. t- a u 



THE PRESENT STATE OF VARIABLE STAR WORK 

 (II). — For the sake of convenience the following survey of 

 variable star work has been arranged under the heading 

 of countries, taken approximately in the order of their 

 respective importance as regards this matter. I have 

 made no attempt to write an historical sketch and, there- 

 fore, have confined myself essentially to present facts. As 

 it may be easily understood, "absolute" completeness in such 

 a work is difficult to attain : many astronomers have made 

 purely accidental discoveries of variable stars in the course of 

 other duties — such as observations of planets, comets, and 

 double stars, zone observations, measures and comparisons of 

 celestial photographs — without being really interested in this 

 branch of astronomy, and it could be hardly possible to include 

 their names here. I am satisfied, however, that no essential 

 fact has been overlooked in the following. 



Germany. — If the height of scientific activity resides in 

 care, spirit of enterprise, continuity, abundance and accuracy 

 of bibliographical sources and especially " thoroughness," 

 rather than in multiplicity of discoveries, one must admit that 

 German astronomers, following the glorious steps of their great 

 Argelander, the initiator of the " science " of variable stars, 

 always took the lead in this branch of astronomy, 



A good deal of this result, in modern years, is undoubtedly 

 due to the \ivid interest shown in stellar photometry by the 

 " Astronomische Gesellschaft," an international association of 

 (principally professional German. Austrian, Scandinavian and 

 Russian) astronomers, established in Leipzig in 1865. The 

 " A.G.," as it is generally named for the sake of brevity, whose 

 star catalogues are well known everywhere, controls three 

 organizations of importance connected with our special 

 subject. 



(1) .\ "Committee on Variable Stars." at present com- 

 posed of Professor N. C. Duner. director of the University 

 Observatory of Upsala (Sweden). Professor Dr. Ernst Hartwig, 

 director of the Remeis Observatory in Bamberg (Bavaria), 

 and Professor Dr. G. Miiller, chief astronomer at the Royal 

 Astrophysical Observatory of Potsdam (Prussia). When, 

 in 1901 (See Astronoiiiical Journal, Nos. 491-492 and 

 Nos. 505-506), Mr. Seth C, Chandler, of Boston, to whom I will 

 refer afterwards, declared that he was going to give up the 

 important and strenuous task of collecting all available 

 information on variable stars, and cease to assign definitive 

 names to those whose elements were sufficiently known, a 

 work which he had carried on for years with a great skill, the 

 .\.Ci. Committee on Variable Stars which, at the time, 

 comprised also the Dutch Professor Oudemans, since deceased, 

 at once took over the matter and has directed it ever since 

 with a great exactness. Professor Miiller especially taking a 

 great share in the work. The Committee has made special 

 and very wise rules (fully explained in Astroiioiiiisclie 

 Xachrichten 171, 347) for the admission of suspected 

 \ariable stars among the number of those to which 

 definitive letters are affixed, the principal of them being 

 that the range of light variation ought to be at least 

 half a magnitude, that the character of this variation 

 must be, at least roughly, indicated, and that it must have 

 been confirmed by at least one other observer than the 

 discoverer. Save some critical views uttered by that other 

 well-known authority, Professor E. C. Pickering (See Annals 

 of Harvard College Observatory, Vol. Iv., page 87), and 

 which serve only to demonstrate the fact that no human work 



