Cetus, the Whale.
This star is called "Myra, the Wonderful" because of its amazing behavior in a period of only eleven months. For three months Myra is visible to the unaided eye; during the other eight it can only be seen in a good telescope. Put in another way—for five months at a time it is completely invisible to the unaided eye; then from a mere speck it slowly brightens until in the course of three months more it has become a star of the 2nd magnitude, although it remains a star of the 2nd magnitude for only a few weeks. This change from a telescopic star of the 9th or 10th magnitude to one of the 2nd magnitude means that Myra must blaze up from 1000 times to 1500 times its ordinary brilliancy! Such a statement may overwhelm the casual reader but we must remember (in order not to become unduly excited) that this star is so far away that such a conflagration would only mean the gradual appearance of a star where none had been visible before, and then its gradual disappearance.
Myra is indeed so far away that we are just 23 years behind time in seeing each explosion, for it takes 23 years for its light to travel to our eyes. If the roar of the conflagration could be heard here, however, the sound would not reach the earth for many millions of years, for sound travels much more slowly than light.
Myra, the wonderful variable star, on the neck of Cetus, the Sea-monster.
Because of the variation of its light, which is very excessive in the case of Myra, this star is called a variable star. Our sun is also a variable star, but it is variable only in a very slight degree as compared with the exuberant combustibility of Myra. But the theory of spots which are believed to be responsible for the almost imperceptible variation in the light intensity of our sun does not altogether explain the phenomenon of Myra's variability and its mystery is still as great as ever.
Thus is ended the story of Perseus and Andromeda and many of the interesting bits of information connected with the constellations of the various characters after they were transferred to the sky.
Three small constellations lie between Andromeda, Cetus and the Square of Pegasus, and a word about them here will help to impress this part of the sky upon the mind without the trouble of carrying maps every time one feels inclined to gaze at the stars. These constellations are Pisces, the Fish; Triangulum, the Triangle and Aries, the Ram.