John Gianvito, age 11, of Staten Island, New York, for his question:
What is the story of Algol?
The average young space ager knows what Algol is and most likely where to find it. But let's un mystify our non celestial readers and politely inform them that Algol is a star. We can make them feel even more comfortable by explaining that the weird behavior of Algol mystified the world's brightest star gazers for untold ages.
The major constellations and their vivid, visible stars were named ages ago, perhaps before the dawn of recorded history. The bright star Algol was given an Arabic name meaning "ghoul" or "ogre." Later generations referred to it as Algol, the Demon Star. This seems a most unlikely name to bestow upon a bright, celestial star, but there was a reason for it. Most of the fixed stars can be depended upon to shine with steady, unchangeable brilliance. Algol does not. Its brilliance fluctuates, growing dimmer and brighter at regular intervals.. This odd behavior can be observed by any keen eyed star gazer without a telescope.
The name Algol, the Demon Star, suggests that its weird character was known to the astronomers of antiquity. We cannot say when this early part of the story began. But about 300 years ago, Algol's off beat behavior again came'to the attention of astronomers, and late in the last century, scientific means were used to explain it down to the last detail. Very often, the answer to a bothersome problem also solves several other tantalizing mysteries. This happened when we solved the secret of Algol. The old Demon introduced us to thousands of similar stars and lent a helping hand to solving the structure of the universe.
The recent chapter in the story of Algol began in 1669, when the variations of its brilliance were verified by an astronomer named Montanari. In 1782, John Goodllllllricke figured Algol's variable period to be two days and 21 hours. After 59 hours, its fairly steady brilliance dims to one third and returns. Goodricke suggested that Algol is really two stars orbiting around each other. He explained the 10 hour lapse as an eclipse that occurs when the dim star passes between us and its bright partner.
This theory was verified in the 1880's and Algol became the first variable star to be classified as an eclipsing binary. Spectroscopes helped in measuring the velocity of the bright star and proved that it approaches and recedes from us in time with the eclipsing schedule. Other techniques were used to measure the size, mass masses and distances of the swinging partners. They are 100 light years away from us and about 13 million miles from each other. The brighter partner is three times wider and 14 0 times more luminous than the sun. The partner that eclipses its brilliance on schedule is larger, much lighter and very dim.
We now know that Algol's odd behavior is by no means a rare celestial performance. At least 3,000 other eclipsing binaries have been classified. Their periods range from about four hours to 27 years, depending upon how widely the swinging partners are separated. The distance between Algol's pair of performers is about one third of the mileage between Mercury and the sun. Their gravitational forces must cause a heaving, havoc of tidal friction on both of the stars.