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==Spica in Culture and History==

==Spica in Culture and History==

The name Spica itself comes from the [[Latin]] phrase ''spica virginis'', meaning "Virgo's ear of wheat (or grain)".  The [[Greeks]] called the star Στάχυς, meaning "ear spike".  In [[Medieval Europe]], the star was referred to as '''Azimech''', from the Arabic word السماك الأعزل ''al-simāk al-a‘zal'', meaning "the defenseless", or as '''Alarph''' "the grape gatherer".  [[Astrology|Astrologers]] at that time viewed Spica as a Behenian fixed star, associated with [[sage]] and [[emerald|emeralds]].  For the [[Chinese]], the star is ''Jiao Xiu 1'' (角宿一), in the Chinese constellation ''Jiao Xiu'' (角宿), the latter translates as "Horn".<ref name="allen">Allen, Richard Hinckley (2003). Star Names and Their Meanings. Kessinger Publishing. pp. 468. ISBN 0766140288</ref>

The name Spica itself comes from the [[Latin]] phrase ''spica virginis'', meaning "Virgo's ear of wheat (or grain)".  The [[Greeks]] called the star Στάχυς, meaning "ear spike".  In [[Medieval Europe]], the star was referred to as '''Azimech''', from the Arabic word السماك الأعزل ''al-simāk al-a‘zal'', meaning "the defenseless", or as '''Alarph''' "the grape gatherer".  [[Astrology|Astrologers]] at that time viewed Spica as a Behenian fixed star, associated with [[sage]] and [[emerald]]s.  For the [[Chinese]], the star is ''Jiao Xiu 1'' (角宿一), in the Chinese constellation ''Jiao Xiu'' (角宿), the latter translates as "Horn".<ref name="allen">Allen, Richard Hinckley (2003). Star Names and Their Meanings. Kessinger Publishing. pp. 468. ISBN 0766140288</ref>

Spica was no doubt known to man since before recorded history.  The first known reference to the star is a temple in [[Thebes]] that was constructed for the [[Egyptian]] goddess Menat (later [[Egyptian_mythology|Hathor]]), was oriented towards Spica as it set in the sky, and was believed built around 3200 BC.  Later, other temples around the [[Mediterranean]] were built with the same orientation, including one in 2000 BC at Tell al Amarna, as well as [[Olympia]] in 1445 BC, and [[Athens]] in 1130 BC, among others. <ref name="allen">Allen, Richard Hinckley (2003). Star Names and Their Meanings. Kessinger Publishing. pp. 468. ISBN 0766140288</ref>  Later, [[Timochares]] studied Spica and Regulus around 300 BC, and using the information from these observations some 150 years later, [[Hipparchus]] was able to discover the [[precession of the equinoxes]].<ref>Evans, James (1998). The History and Practice of Ancient Astronomy. Oxford University Press. pp. 259. ISBN 0195095391</ref>  Later, during the [[Renaissance]], [[Copernicus]] used Spica for his own observations while researching the Earth's precession.<ref>http://articles.adsabs.harvard.edu//full/1943JRASC..37..129R/0000129.000.html</ref>

Spica was no doubt known to man since before recorded history.  The first known reference to the star is a temple in [[Thebes]] that was constructed for the [[Egyptian]] goddess Menat (later [[Egyptian mythology|Hathor]]), was oriented towards Spica as it set in the sky, and was believed built around 3200 BC.  Later, other temples around the [[Mediterranean]] were built with the same orientation, including one in 2000 BC at Tell al Amarna, as well as [[Olympia]] in 1445 BC, and [[Athens]] in 1130 BC, among others.<ref name="allen"/>  Later, [[Timochares]] studied Spica and Regulus around 300 BC, and using the information from these observations some 150 years later, [[Hipparchus]] was able to discover the [[precession of the equinoxes]].<ref>Evans, James (1998). The History and Practice of Ancient Astronomy. Oxford University Press. pp. 259. ISBN 0195095391</ref>  Later, during the [[Renaissance]], [[Copernicus]] used Spica for his own observations while researching the Earth's precession.<ref>http://articles.adsabs.harvard.edu//full/1943JRASC..37..129R/0000129.000.html</ref>

==Star System==

==Star System==

Spica is actually a binary star system, with a combined apparent magnitude of 1.04.  The primary star is a blue-white giant or subgiant star of spectral type B1 III-IV, while its companion is a blue-white main sequence dwarf of spectral type B2 V. As the two stars are only 0.12 AU apart, they complete an orbit of each other every 4.0145 days. <ref>http://domeofthesky.com/clicks/spica.html</ref> It was commonly believed the variation of the apparent brightness of the two stars was caused by one regularly eclipsing the other from our vantage point on Earth.  The variation is actually caused by the tidal distortion the stars afflict on each other, altering the apparent diameters to an observer on [[Earth]] as they orbit, which varies the apparent magnitude by around 0.03.  In addition, the primary star is a [[Beta Cephei]] variable star, and pulsates in brightness with a regular variation of 0.015 magnitudes every 4.2 hours.<ref name="illinois">http://stars.astro.illinois.edu/sow/spica.html</ref>

Spica is actually a binary star system, with a combined apparent magnitude of 1.04.  The primary star is a blue-white giant or subgiant star of spectral type B1 III-IV, while its companion is a blue-white main sequence dwarf of spectral type B2 V. As the two stars are only 0.12 AU apart, they complete an orbit of each other every 4.0145 days.<ref>http://domeofthesky.com/clicks/spica.html</ref> It was commonly believed the variation of the apparent brightness of the two stars was caused by one regularly eclipsing the other from our vantage point on Earth.  The variation is actually caused by the tidal distortion the stars afflict on each other, altering the apparent diameters to an observer on [[Earth]] as they orbit, which varies the apparent magnitude by around 0.03.  In addition, the primary star is a [[Beta Cephei]] variable star, and pulsates in brightness with a regular variation of 0.015 magnitudes every 4.2 hours.<ref name="illinois">http://stars.astro.illinois.edu/sow/spica.html</ref>

The brighter primary has 10.5 times to [[Sun|Sun's]] mass and 7 times its diameter, with a surface temperature at 22,400 K. Because of the star's large mass, it will most likely end its life as a [[supernova]].  The companion star 4 times the Sun's diameter and six times its mass, with a cooler surface temperature of 18,500 K. Combined, the two [[star|stars]] have 2200 times the Sun's visible luminosity.  However, because most of the radiation from the two stars are in the [[ultraviolet]], the primary alone actually has a total luminously 12,100 times that of our Sun, while the companion is 1,500 times as bright in total luminosity.<ref name="illinois">http://stars.astro.illinois.edu/sow/spica.html</ref>

The brighter primary has 10.5 times to [[Sun|Sun's]] mass and 7 times its diameter, with a surface temperature at 22,400 K. Because of the star's large mass, it will most likely end its life as a [[supernova]].  The companion star 4 times the Sun's diameter and six times its mass, with a cooler surface temperature of 18,500 K. Combined, the two [[star]]s have 2200 times the Sun's visible luminosity.  However, because most of the radiation from the two stars are in the [[ultraviolet]], the primary alone actually has a total luminously 12,100 times that of our Sun, while the companion is 1,500 times as bright in total luminosity.<ref name="illinois"/>

[[Category:Astronomy]]

[[Category:Astronomy]]