Spica (αVirginis) is a brilliant first_magnitudestar, believed to be the star that provided Hipparchus with the data which enabled him to discover precession of the equinoxes. A temple to Menat (an early Hathor) at Thebes was oriented with reference to Spica when it was constructed in 3200 BC and, over time, precession resulted in a slow but noticeable change in the location of Spica relative to the temple. Nicolaus Copernicus made many observations of Spica with his home-made triquetrum for his researches on precession.
The name Spica derives from Latinspica (an ear of grain, usually corn or wheat).
Spica is an eclipsing binary like Algol. Its apparent magnitude varies between +0,92 and +0,98, with a period of 4.0142 days. This slight dip in magnitude is barely noticeable visually.
Located close to the Ecliptic, Spica can be eclipsed by the Moon and (rarely) by the planets. The last planetary eclipse of Spica occurred when Venus passed in front of the star (as seen from Earth) on November 10, 1783. The next eclipse will occur September 2, 2197, when Venus again passes in front of Spica.
An easy way to find Spica is to follow the arc of the handle of the Big Dipper to Arcturus (α Boötis), and then continue on the same distance to Spica.
The stars gamma Virginis, eta Virginis, beta Virginis, nu Virginis, and omicron Virginis form the virgin's head: all of these stars are of fourth magnitude except gamma Virginis which is of third magnitude.
The stars gamma Virginis, delta Virginis, zeta Virginis, alphaVirginis, and theta Virginis form the virgin's blouse: alphaVirginis, also known as Spica, is of the first magnitude, whereas zeta Virginis is of the third magnitude.
The stars alphaVirginis, zeta Virginis, tau Virginis, iota Virginis, and kappa Virginis form the virgin's skirt: the last three stars being of the fourth magnitude.
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