POPULAR SCIENCE 615 



to the brilliant luminary that heralded the birth of Christ our 

 Lord. The star is prominently figured in the constellation of 

 Cassiopeia in Beyer's Uranometria, published in a.d. 1661. 



Very wonderful, too, must have been the appearance of the 

 Venus-like nova of a.d. 1604, witnessed and described by an 

 equally famous astronomer, the illustrious Kepler. This star 

 was seen in the constellation of Ophiuchus. Struck by its intense 

 brilliancy, Kepler thereupon broached a theory that the Star 

 of Bethlehem was to be explained by the appearance of a new 

 star, combined with a conjunction of the brilliant planets Mars, 

 Jupiter, and Saturn in the same region of the sky. 



Yet another remarkable new star, discovered in the same 

 century, was Anthelm's nova of a.d. 1670, which, appearing 

 near /3 Cygni, was to be seen for two years, the brilliancy 

 fluctuating in a noticeable manner. No other new star was 

 seen for a period of one hundred and seventy-eight years, 

 the next recorded discovery being that of a second new star 

 in the constellation of Ophiuchus, by Hind, in the year 1848. 

 Since that date no less than twelve novae have shone out as 

 visible to the naked eye, while telescopic discoveries have been 

 greatly multiplied. 



Up to July 191 7 thirty-two of these objects were known, 

 and all of them, with three exceptions, were situated in the 

 Milky Way. One exception was the variable star T Coronae, 

 which in 1866 rose from the ninth to the fourth magnitude in 

 a few hours. Though similar to a nova, it was not a true 

 member of the type. It was the first new star submitted to 

 spectroscopic analysis, by Sir William Huggins, and showed a 

 composite spectrum of dark absorptions and of bright radiations. 

 The other two exceptions to this concentration of new stars 

 in the plane of the Milky Way were two novae, discovered in 

 spiral nebulae. The more remarkable of these two was that 

 discovered in the heart of the great nebula in Andromeda in 

 the year a.d. 1885. It shone with a distinctly green tinge of 

 light in a continuous spectrum. It was the first new star 

 examined spectroscopically by the writer. Vogel's observations 

 of the nova of 1876, in Cygnus, had demonstrated a transition 

 of the spectrum frorri a double spectrum of absorptions and 

 corresponding radiations, mainly due to hydrogen, until a phase 

 was reached when the chief green ray of the nebular spectrum 

 alone survived. Burnham, observing the star at the Lick 

 Observatory in 1891, stated that it appeared to be like a small 

 nebula. In the period from July 191 7 to the end of 191 9 no 

 less than seventeen new stars had been discovered. Of these 

 last, fifteen are situated in spiral nebulae, and of these again 

 eleven have been found in the central condensation of the 

 Andromeda nebula. 



