December 8, 1892] 



NATURE 



m 



THE NEW STAR IN THE CONSTELLATION 

 OF AURIGA.-^ 



'T'HE appearances which the new star has presented were 

 ■*• exceedingly remarlcable, and observations, both spectro- 

 scopic and photometric, were far more numerous than have been 

 obtained during former occurrences of this kind. The latter 

 have been sufficient to establish the unsuitability of several 

 explanations which have been suggested with regard to 

 former new stars, suggestions which at the time appeared 

 more or less plausible. On the other hand, however, it is 

 very difficult to establish, from the publications of observers 

 up to the present time, all details required for a general 

 proof of a definite hypothesis. It appears to me appro- 

 priate to suggest a new attempt at explanation, which seems 

 to tally better than others with the principal results of observa- 

 tion, the final tests of which hypothesis must, however, for the 

 present remain a matter for the future. But if this attempt 

 should in the present instance meet with difficulties — a case which 

 I admit to be possible, if not probable — it yet deserves a some- 

 what more detailed explanation, because it thoroughly takes 

 account of, as I believe, possible conditions, and therefore 

 certainly contains a possible hypothesis with regard to the ap- 

 pearances of certain new stars. In the following remarks I 

 shall strictly adhere to the facts which are to be considered, 

 according to the statements of the observers, as the result of 

 their observations, whereas a proof of the latter is beyond the 

 limit of this article. I may here mention that I have already 

 suggested the most essential of the following remarks in March 

 of the present year.^ 



The chief results of observations, which may be said to con- 

 tain the characteristics of all the appearances, are : — 



1. According to Herrn Lindeman * the light-curve of the 

 Nova pre-ented the following appearances : — 



"From February I to 3 the photometric curve rises quickly 

 to a brightness of 4.7m., then gradually sinks till February 13, 

 and then quicker until February 16 to 5.8m., reaches a second 

 maximum of 5.14m. on February 18, has a second minimum on 

 February 23, likewise of 5. 8m., and then a third maximum on 

 March 2 again of 5.4m., upon which it sinks till March 6, 

 slowly at first, and then quicker, in a straight line till March 22 

 down to 9.3". I may here add that from the photo3;raphs 

 taken at Harvard College, it was possible to show that the star 

 became visible from the beginning of December, 1891, that 

 already in the period of time December 20-22 it showed a 

 maximum of brightness which reached almost, but apparently 

 not entirely, a maximum on February 3. 



2. The spectrum of the Nova was most remarkable. Trof. 

 Vogel, in summing up the results obtained at Potsdam,* 

 writes : — 



"The observations have led to the exceedingly interesting 

 result that the spectrum of the Nova consists of two superposed 

 spectra, and that a number of lines, especially those of hydro- 

 gen, which appear bright in one spectrum and dark in the 

 other, are closely adjacent to one another. This fact admits of 

 hardly any other explanation than the presence of two bodies, 

 the component motions of which in the line of sight are very 

 considerable, . . . The bodies separate from one another with 

 a relative velocity which during four weeks' observations (in 

 February) suffisred no appreciable change, and which amounted 

 to at least 120 miles per second." It may be further added '^ 

 that among the very broadened bright lines there were noted 

 several intensity maxima, two being especially sti iking. 



It has been suggested as an explanation of the facts of observa- 

 lion that two heavenly bodies have passed very close by one 

 another, and that thus changes in their atmospheres have arisen 

 which have caused the sudden brightening up of the bodies. The 

 above hypothesis is, however, in this form too vague to be fol- 

 lowed in detail. In reverting to an idea of Klinkerfues, it is 

 true that a more distinct picture of the whole occurrence has 

 been drawn, by assuming tidal effects of the two bodies upon 

 each other : in this manner where the tidal crests of the atmo- 

 sphere appear, there the darkenings take place by absorption, 

 and where the ebb predominates a brightening is the result, 



' Translation of an article by H. Seelinger, in Astronomische Nac/t- 

 rkhten (No. 31 18),. 



2 "On a General Problem of the Mechanics of the Heavens," p. a3. 

 (Miinchen, 1892.) 



3 ^str Nach., No. 3094. 



4 Vierteljahrsschrift der Aitr. GeulUch , Band 27, p. 141. 

 3 Astn Nachr., ■iojt), p. no. 



NO. 1206, VOL. 47] 



because here the absorbing strata of the atmospheres are less 

 powerful. It must be mentioned, however, that the statical 

 theory of Ebb and Flow that has been applied is altogether 

 inappropriate to give an idea of the deformations which doubt- 

 lessly occur at such a near proximity. The effect of the 

 two heavenly bodies on each other in Nova Aurigae, as is 

 still to be shown, would have to be one that is almost always 

 suddenly appearing an I immediately afterwards vanishing. 

 Moreover it must not be overlooked, that with incandescent 

 bodies their atmospheres must be regarded as outward shells 

 which quite gradually emerge into denser strata, while these 

 also are deformed in a lesser degree. In other respects, too, it 

 will be difficult to explam the appearances of a new star as 

 a consequence only of the effects of absorption of atmospheres. 

 It has also been assumed for the most part that besides these 

 (absorptions), eruptions of gas from the centre of the body take 

 place. This assumption, it is true, contains nothing impos- 

 sible, but without a definite form it hardly admits of discussion. 

 At all events it will be necessary to suggest further hypotheses 

 in order to apply this attempt at explanation to single cases. 

 Moreover, it remain-; yet unexplained why in Nova Aurigae the 

 one spectrum is chiefly an absorption spectrum and the other a 

 gas spectrum. By special assumptions this difficulty can be 

 certainly eliminated, but it is not very probable that on this 

 account confidence can be placed in the correctness of the 

 hypothesis. 



Other facts appear, however, in the case of Nova 

 Aurigae which do not speak in favour of this hypothesis, 

 however generally it may be expressed. It is at least 

 very striking that just in this case such enormously great 

 velocities of cosmical bodies appear, such as have hitherto 

 not been found anywhere else. The occurrences of these 

 velocities must therefore be numbered among the facts to 

 be explained. Further on formulae will be given from which, 

 at least to a certain degree, the mechanical conditions of the 

 close approach of two bodies can be computed. From this it 

 follows that in the case of Nova Aurigae the two bodies can 

 describe a parabola round each other only if their masses are 

 much larger than 15,000 times the sun's mass. For a hyper- 

 bolic movement one can obtain an essentially smaller value of 

 the mass, by assuming that the enormous relative velocity of 

 120 miles observed has been ; roduced to a small degree by 

 attraction and has existed almost entirely from the beginning. 

 Thus the choice is left between the assumption of extremely 

 large masses or the giving up of an explanation of the great 

 relative velocity. Neither of these two assumptions contain, it 

 is true, an impossibility, but I do not think that doubtful 

 proofs for the correction of the hypothesis can be noticed in 

 either of them. According to my opinion they rather render it 

 (the hypothesis) very little plausible. 



The formulae already mentioned indicate what will be ex- 

 plained further on, namely, that the supposed effect of the two 

 bodies, in the case in hand, must have taken place very quickly 

 indeed, perhaps even in the period of a few hours. This effect 

 must necessarily have occurred upon the first brightening up 

 (beginning of December 1891). Why then the Nova attained 

 several weeks later (beginning of February 1892) a second 

 maximum, and to all appearances a greater maximum, and why 

 the light-curve sank only very little till the beginning of March 

 but afterwards very rapidly, seems to me, on the ground of the 

 hypothesis in question, to be explainable only with great diffi- 

 culty, if it can be explained at all. At all events, this difficulty 

 will remain unless it be altogether removed in detail. 



The difficulties hinted at above entirely disappear in the 

 following supposition. There is no doubt, especially in accord- 

 ance and with the results obtained from stellar photographs, in 

 which Mr. Max Wolf has co-operated, that space is entirely 

 filled with more or le<s extensive formations of very thinly 

 scattered matter. With regard to their physical properties, 

 these formations will probably show very varied constitutions, 

 the reason for which we will leave an open question, as we do 

 not wish to investigate it here. It is itself not very improbable 

 that a htavenly body should get into such a cloud, but in any 

 case it is more probable than the grazing together 0! two com- 

 pact bodies, as is required in the above-discussed hypothesis. 

 As soon now as the body commences to enter a cosmic cloud 

 a sur'ace heating will be set up at once, and indeed it must be 

 so, whatever may be the constitution of the thinly-scattered 

 matter. In consequence of this heating, the products of vapour- 

 izaation will form round the body ; these will partly be separated 



