Science Fair Project Encyclopedia
Spica
Spica (α Vir / α Virginis / Alpha Virginis) is the brightest star in the constellation Virgo, and one of the brightest stars in the nighttime sky.
Spica is 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 Latin spīca virginis "Virgo's ear of grain" (usually 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, and then continue on the same distance to Spica.
Some facts about Spica
- Distance from Earth : 262 light-years
- Spectral type: B1 V
- Radial velocity: 1 km/s
- Proper Motion: 0.053 arcsecs/year
- Apparent Visual Brightness (Sirius A = 1): 0.108
- Apparent Visual Magnitude: 0.98
- Absolute Visual Magnitude: -3.55
- Luminosity: 2.5e4 Solar Luminosities
External links
- http://slo-astro.lmbitea.si/spika.html the first Slovene astronomical magazine, edited by Bojan Kambič and published since 1995 (Slovene)
- http://astrospica.com Site featuring beautiful images from the space whose name its devoted to the Spica star. (Spanish)
- http://www.marco-peuschel.de/merkurvenushellesterne.html Tabulates past and future eclipses of bright stars by the inner planets. (German).
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