Algol, the Halloween star

[Boris_Badenov]

Algol <br />The Halloween sky offers up a star that medieval astrologers considered the most dangerous in the entire sky. Appropriately, the star's name -- Algol -- comes from an Arabic name that means "the ghoul."<br /><br />Algol may have developed that demonic reputation because its light varies -- it gets brighter and fainter. Lots of other stars vary, too, but none is as obvious as Algol.<br /><br />In the 1780s, two young astronomers in England began to study Algol and other variable stars.<br /><br />In 1783, one of those astronomers -- a deaf and mute 18-year-old, John Goodricke -- discovered that Algol's light varies every two days and 21 hours.<br /><br />The length of the variation was a key clue to its cause. Goodricke's older friend, Edward Pigott, suggested that Algol consists of two stars in orbit around each other. When the fainter of the two stars passes in front of the brighter one, it cuts off the brighter star's light, causing Algol to fade. It turns out that he was right. And since then, astronomers have discovered many more of these "eclipsing binaries."<br /><br />You can see Algol tonight. With the help of a star chart, look northeast around nine o'clock for the constellation Perseus. Normally, Algol is about as bright as the brightest star in Perseus. But during an eclipse, it gets dimmer -- as though the demon eye of Perseus were winking at the trick-or-treaters on a Halloween night.<br /> <div class="Discussion_UserSignature"> <font color="#993300"><span class="body"><font size="2" color="#3366ff"><div align="center">. </div><div align="center">Never roll in the mud with a pig. You'll both get dirty & the pig likes it.</div></font></span></font> </div>