Page:The Music of the Spheres.djvu/78

 grewsome head of the Gorgon Medusa where ever after it has flashed and faded in the most eerie fashion.

The mystery of this winking star was not discovered until 1889. Then Vogel found that the periodical change of brightness in Algol is caused by a huge dimly lighted sun,—relatively dark compared with Algol,—which revolves around the major sun at a distance of only 3,000,000 miles. (The earth revolves at a distance of 93,000,000 miles from our sun.) Every time this darker body passes between Algol and the earth, five-sixths of the light from Algol is cut off, thus making it appear to blink. Vogel also found, through the aid of the spectroscope, the diameter and mass of these stars. Algol was found to be about one million miles in diameter with a mass less than half that of the sun while its companion was found to be about 800,000 miles in diameter with a mass about one fourth that of our sun.

Thirty stars are now known to be of the Algol type. One of the most remarkable of these, V. Puppis, was found to be in the southern hemisphere and was carefully examined by. This star has a light variation of only 1½ days and is believed to whirl so closely to its companion that it is in actual contact.

The most favorable seasons for seeing Algol during the early evening are in the autumn, winter and early spring; in the autumn, low in the northeast, when it rises at sunset in the middle of September; in the winter, high up in the north, not far from the zenith; and in the spring, low down in the northwest. At the correct time it is possible for anyone to see its change in brilliancy although the best time to watch for this is during September and October. Algol rises at sunset in the middle of September and consumes 9 hours and 12 minutes in reaching the meridian. To best appreciate the change in this star compare it with the stars near by, especially to the 4th magnitude star that lies quite near to it.