Algol, a variable star in the constellation Perseus. (A variable star is one that changes in brightness.) Algol, which was observed by the ancient Greeks and named by the Arabs, is now known to be a complex system of at least four stars revolving around one another. A pair of the stars forms an eclipsing binarytwo stars that pass in front of each other in turn, causing a periodic (cyclical) dimming of their combined light. Algol dims regularly every 21 days and 21 hours.
The moon is often the largest object in the sky outside of the sun. What is the moon made of, how did it form -- and why do people blame it for their strange behavior?
One tragic, moonless night in April 1912, the Titanic slid into the depths of the North Atlantic Ocean -- for good. A crew of Texas State academics suggested that Earth's favorite satellite may have some explaining to do.