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THE POPULAR SCIENCE MONTHLY 



" The spectrum of the variable star of Corona Borealis is found to consist of 

 two superposed spectra, the one made up of four bright lines, and the other resem- 

 bling the solar spectrum, each resulting from the decomposition of a group of 

 luminous rays independent of the light which produces the other. The continuous 

 spectrum, furrowed with groups of dark rays, indicates the presence of a photo- 

 sphere of incandescent matter, almost certainly solid or liquid, and surrounded 

 by an atmosphere of cooler vapors, which produce by absorption the groups of 

 darker lines. So far the constitution of this star resembles that of the sun ; but 

 it offers an additional spectrum composed of bright lines. Here, then, is a second 

 source of special light, and this source must le a luminous gas. Furthermore, 

 the two principal bright lines of this spectrum show that this gas consisted 

 mainly of hydrogen ; and their great brightness proves that the temperature of 

 the luminous gas was higher than that of the photosphere. These facts, taken 

 in connection with the suddenness of the outburst of light in the star, its im- 



FiG. 1. Spectrum op the Variable Star in Corona Borealis. (From Euggins and Miller.) 



mediate and rapid diminution of brightness, and its decline, in the course of 

 twelve days, from the second to the eighth magnitude, lead us to the conclusion 

 that the star was suddenly enveloped in hydrogen-flames. Possibly it was the 

 scene of some mighty convulsion, with disengagement of an enormous amount 

 of liberated gas. A great portion of this gas was hydrogen, which burned on 

 the surface of the star by combining with some other element. The light given 

 forth by this flaming gas was characterized by the spectrum with bright lines. 

 The spectrum of the other portion of the star's light probably showed that this 

 terrible conflagration of gas had surcharged and rendered more" vividly incan- 

 descent the solid matter of the photosphere. "When the free hydrogen had been 

 exhausted, the flame died away by degrees, the photosphere became less lumi- 

 nous, and the star returned to its former state. . . . We must not forget," adds 

 Mr. Huggins, " that light, though it travels with such great velocity, neverthe- 

 less requires a certain time to come to us from the star. Hence this grand physi- 

 cal convulsion, though new to us, was a thing of the past as regards the star it- 

 self. In 1866 the star had already for years been in the new conditions produced 

 by this violent catastrophe." 



The solar protuberances had not as yet been directly analyzed in 

 1866 ; it was not yet known that a continuous stratum of incandescent 

 hydrogen envelops the bright photosphere of the sun, and that the 

 emission of this gas, in the form of irregular jets, undergoes in the 

 sun variations, phases, which are at least so far related to the sun- 

 spots as to be coincident with tliem. What mighty physical revolu- 



