The variability of Algol ((3 Persei) was discovered in 1783 by John Goodricke (1764-1786), but, judging from its name, which signifies ' ` the demon," it seems possible that its peculiarity may have been known to the ancient astronomers.
For nearly three centuries after these two remarkable stars no nova attained a brilliancy greater than that of the ordinary stars, until in 1901 Nova Persei appeared.
In the case of this star there is evidence that the outburst must have been extremely rapid, for the region where Nova Persei appeared had been photographed repeatedly at Harvard during February, and in particular no trace of the star was found on a plate taken on the 19th of February, which showed eleventh magnitude stars.
On the 21st of August, six months after the discovery of Nova Persei, C. Flammarion and E.
In this connexion it may be noted that the spectrum of Nova Persei, after passing through a stage in which it resembled that of a planetary nebula, has now become of the Wolf-Rayet type.