240 ANNUAL OF SCIENTIFIC DISCOVERY. 



" The old thenrios rcspcctin;;: these stranp^o objects must be re- 

 jected. We cannot believe with Tycho Biahe that objects so 

 ephemeral are new creations, nor with Riccioli tiiat they are stars 

 brilliant on one side only, wliiih have been siiddi'iily tnined 

 round by the Deity. Tlie theory that they have suddenly darted 

 towards us with a velocity jjreater than tliat of light, from a re- 

 gion of remote invisibility, will not now find suj)|>orters. 



"On the I21I1 of May last, a star of the si-eond ina^nitutle sud- 

 denly burst fortli in the constellation of the Northern Crown. 

 Tiianks to the kindness of the discoverer of this phenomenon, 

 Mr. Hirniin<,^hani, of Tuam, 1 was enabled, eon jointly with Dr. 

 Miller, to examine the speetrum of this star on liie Kith of May, 

 when it had not fallen much below the third iua<j;nilude. 



*' The spectrum of tliis star consists of two distinct spectra. 

 One of tliese is formed by four briirht lines. The other spec- 

 trum is analogous to tlie sj)eetra of the sun and stars. 



"The.se two speetra represent two distinct sources of light. 

 Each speetrum is f(jrmed by tiie decomposition of light, which is 

 independent of the light winch gives birth to the other spectrum. 



"Tlie continuous speetnnn, erowded with groups of dark lines, 

 shows that there exists a photosphere of incandescent solid or 

 liquid matter ; further, that there is an atmosphere of cooler 

 vapors, which give rise by absorption to the groiii)s of dark lines. 



"So far, the constitution of this object is analogous to that 

 of the sun and stars, but in addition there is the second spec- 

 trum, which consists of bright lines. There is therefore a second 

 and distinct somve of light, and this must be, as the character of 

 the sjieetrum shows, luminous gas. Now the position of the two 

 principal of the bright lines of this spectrum informs us that one 

 of the luminous gases is hydrogen. The great brightness of 

 these lines shows that the luminous gas is hotter than the photo- 

 sphere. These facts, taken in connection with the suddenness of 

 the outburst of light in the star, and its immediate veiy rajjid 

 decline in briirjitness from the second magnitude down to the 

 eighth ma":nitude in twelve davs, suirgested to us the startlins: 

 speculation tliat the star had become suddenly enraptin tlie Hames 

 of burning hydrogen. In consequence, it may be, of some great 

 convulsion, enormous quantities of gas were set free. A large 

 part of this gas consisted of hydrogen, which was burning about 

 the star in combination with some other element. This liaming 

 gas emitted the light represented by the spectrum of bright lines. 

 The increased brightness of the spectrum of the other jjart of 

 the star's light, maj' show that this fierce gaseous conflagration 

 had heated to a more vi\id incandescence the solid matter of the 

 l)hotosphere. As the free hydrogen became exhausted, the flames 

 gradually abated, the photosphere became less vivid, and the star 

 waned down to its former brightness. 



" We must not forget that light, though a swift messenger, re- 

 quires time to pass from the star to us. The great physical con- 

 vulsion, which is new to us, is already an event of the past with 

 respect to the star itself. For years the star has existed under the 

 new conditions which followed this fiery catastrophe. 



