NATURE 



413 



THURSDAY, SEPTEMBER 13, 1877 



STAR OR NEBULA ? 



FOLLOWING close upon the publication of Dr. 

 \'ogers paper on the new star in Cygnus, Lord Lind- 

 say has communicated an interesting letter to the Times 

 announcing the fact that the new star has now put on the 

 appearance presented ordinarily by the so-called plane- 

 tary nebula;. 



Of all the lines chronicled by Cornu and Vogel only 

 one remains, that namely which the latter observer 

 showed to be constantly increasing in brightness while 

 all the rest were waning, and which, moreover, as Vogel 

 also distinctly showed, is coincident in position in the 

 spectrum with that observed in the majority of the 

 nebulce. 



The observations of such rare phenomena as the so- 

 called new stars, are of such vast importance, and will no 

 doubt ultimately provide us with a clue to so many others 

 of a different order, that we may well congratulate our- 

 selves that the recent Nova was so well watched, and that 

 there is such perfect completeness and unity in the chain 

 of recorded facts. 



It should have been perfectly clear to those who 

 thought about such matters that the word star in such a 

 case is a misnomer from a scientific point of view, 

 although no word would be better to describe it in its 

 popular aspect. The word is a misnomer for this reason. 

 If any star, properly so called, were to become " a world 

 on file,'' were to " burst into flames," or in less poetical 

 language, were to be driven either into a condition of 

 incandescence absolutely or to have its incandescence 

 increased, there can be little doubt that thousands or 

 millions of years would be necessary for the reduction of 

 its light to the original intensity. 



Mr. CroU has recently shown that if the incandescence 

 observed came for instance from the collision of two stars, 

 each of them half the mass of the sun, moving directly 

 towards each other with a velocity of 476 miles per 

 second, light and heat would be produced which would 

 cover the present rate of the sun's radiation for a period 

 of 50,000,000 years. 



A very different state of affairs this from that which 

 must have taken place in any of the Novas from the time 

 of Tycho to our own, and the more extreme the difference 

 the less can we be having to deal with anything like a 

 star properly so called. 



The very rapid reduction of light in the case of the new 

 star in Cygnus was so striking that I at once wrote to Mr. 

 Hind to ask if any change of place was observable, 

 because it seemed obvious that if the body which thus put 

 on so suddenly the chromospheric spectrum were single, 

 // might only weigh a Jau tons or even hundiedweiglits, 

 and being so small might be very near us. Mr. Hind's 

 telescope was dismounted, and I have not yet got any 

 information as to change of position ; and as I am now 

 writing in the Highlands, away from all books, I have no 

 opportunity of comparing the position now given by Lord 

 Lindsay in R.A. 2ih. 36m. 52s., Dec. -I- 42° 16' 53", with 

 those given on its first appearance by Winnecke and 

 others. 



Vol, XVI, — No, 411 



We seem driven, then, from the idea that these pheno- 

 mena are produced by the incandescence of large masses 

 of matter, because if they were so produced, the running 

 down of brilliancy would be exceeding slow. 



Let us consider the case, then, on the supposition of 

 small masses of matter. Where are we to find them ? 

 The answer is easy ; — in those small meteoric masses 

 which an ever-increasing mass of evidence tends to 

 show, occupy all the realms of space. 



In connection with this, perhaps I may be permitted to 

 quote the following from one of my " Manchester 

 Lectures'" : — 



" There is one point to which I think I may be per- 

 mitted to draw your attention, although at present it rests 

 merely upon an unendorsed observation of my own. I 

 thought it would be worth while to try what would happen 

 if 1 inclosed specimens of meteorites, taken at random, 

 in a tube from which I subsequently exhausted the air by 

 a pump. After the pumping had gone on for some con- 

 siderable time, of course we got an approach to a 

 vacuum ; and arrangements were made by means of 

 which an electric spark could pass along this apparent 

 vacuum, and give us the spectra of the gases evolved 

 from the meteorites. Taking those precautions which 

 are generally supposed to give us a spark of low tempera- 

 ture, and passing the current, we got a luminous effect 

 which, on being analysed by the spectroscope, gave us 

 that same spectrum of hydro-carbon which ^ir. Huggins, 

 Donati, and others have made us perfectly familiar with 

 as the spectrum of the head of a comet. There, then, we 

 get the atmosphere of meteorites, not necessarily car- 

 bonaceous meteorites, but meteorites taken at random ; 

 and this atmosphere is exactly what we get in the head of 

 a comet. 



" Now let me go one step further ; and to take that step 

 with advantage, allow me to refer to another point .... 

 that whereas Schiaparelli has connected meteorites and 

 falling stars with comets. Professors Tait and Thomson, 

 on the other hand, have connected comets with nebuire, 

 both of them being, according to those physicists, clouds 

 of stones. Now how was one to carry these spectroscopic 

 observations into the region of the nebuki; ? A Leyden 

 jar was included in the circuit, and we had what is gene- 

 rally supposed to be an electric current giving us a very 

 much higher temperature than we had before. What, then, 

 was the spectrum ; the spectrum, so far as the known 

 lines were concerned, was the spectrum which we get 

 from the nebula; ; for the hydro- carbon spectrum, which 

 we get from the atmospheric meteorites at a low tempera- 

 ture, was replaced by the spectrum of hydrogen ; the 

 spectrum of hydrogen coming, of course, from the de- 

 composition of the hydro-carbon, with the curious, but 

 at present unexplained, fact that we got the spectrum 

 indications of h\drogen without indications of carbon. 

 In my laboratory work I have come across other curious 

 cases in which compound vapours, when dissociated, only 

 gave us one spectrum at a time — by which I mean that in 

 a vapour consisting of two well-known substances, under 

 one condition we only get the spectrunr of one substance, 

 and under another condition we get the spectrum of the 

 other substance alone, so in others again of both com- 

 bined. The evidence seems, therefore-— though I do not 

 profess to speak with certainty — entirely in favour of the 

 ideas of Sir Wilham Thomson and Prof. Tait on the one 

 hand, and of Schiaparelli on the other. I note this 

 because I shall have again to refer to the conclusion to be 

 drawn from it, namely, that there is probably an intimate 

 connection between nebulse, comets, meteorites, and 

 falling stars." 



I have given the above extract to show that a mass of 

 meteorites at a temperature higher than that found to 



