Spica

Spica is the brightest star in Virgo and the 15th brightest in the night sky at magnitude 0.98. It is a blue giant of spectral type B1III-IV, located about 250 light-years from Earth. Spica is actually a close spectroscopic binary: two hot stars orbiting each other every 4.01 days at a separation of only about 0.12 AU. The primary is about 10 times the mass of the Sun and 12,000 times more luminous. The two stars are so close that they are tidally distorted into egg shapes.

Spica is easy to find using the arc-to-Arcturus, spike-to-Spica mnemonic — follow the arc of the Big Dipper's handle through Arcturus and continue the curve to reach Spica. Its blue-white color contrasts sharply with the orange of nearby Arcturus. Spica is a useful reference star for the zodiac, as planets and the Moon frequently pass near it along the ecliptic. Best observed from March through July.

The name Spica comes from the Latin 'Spica Virginis' meaning 'ear of grain,' as it represents the sheaf of wheat held by the constellation Virgo. Hipparchus used observations of Spica around 130 BC to discover the precession of the equinoxes — one of the most important discoveries in ancient astronomy. Nicolaus Copernicus also observed Spica to refine his understanding of precession.