Algol

Eclipsing binary, a pair of orbiting stars in the constellation Perseus, the fainter one of which eclipses the brighter one every 69 hours, causing the apparent brightness of the pair to drop by two-thirds.

The brightness changes were first explained in 1782 by English amateur astronomer John Goodricke. He pointed out that the changes between magnitudes 2.2 and 3.5 repeated themselves exactly after an interval of 2.867 days and supposed this to be due to two stars orbiting round and eclipsing each other.

This was the first such eclipsing binary to be recognized. Later, more refined observations showed that there was a third fainter star that revolved round the brighter pair in 1.87 years.

ALGOL

In computing, an early high-level programming language, developed in the 1950s and 1960s for scientific applications. A general-purpose language, ALGOL is best suited to mathematical work and has an algebraic style. Although no longer in common use, it has greatly influenced more recent languages, such as Ada and Pascal.