Spica
From Wikipedia, the free encyclopedia
 Spica in conjunction with the Sun (the dot below the Sun, not the brighter dot to the left of the Sun) each year around 17 October. Photo: NASA SOHO. |
|
| Observation data Epoch J2000 |
|
|---|---|
| Constellation | Virgo |
| Right ascension | 13h 25m 11.6s |
| Declination | −11° 09' 41" |
| Apparent magnitude (V) | +1.04 |
| Spectral Characteristics | |
| Spectral type | B1III-IV/B2V |
| U-B color index | −0.93 |
| B-V color index | −0.13 |
| Variable type | β Cep, Rotating ellipsoid |
| Astrometry | |
| Radial velocity (Rv) | +1.0 km/s |
| Proper motion (μ) | RA: −42.50 mas/yr Dec.: −31.73 mas/yr |
| Parallax (π) | 12.44 ± 0.86 mas |
| Distance | 260 ± 20 ly (80 ± 6 pc) |
| Absolute magnitude (MV) | −3.55 |
| Physical Characteristics | |
| Mass | 11/7 M☉ |
| Radius | 7.8/4.0 R☉ |
| Luminosity | 13,400/1,700 L☉ |
| Temperature | 22,400/18,500 K |
| Metallicity | |
| Rotation | |
| Age | years |
| Other designations | |
- For other uses, see Spica (disambiguation).
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.
In Chinese astronomy, the star is known as Jiao Xiu 1 (角宿一) in Jiao Xiu, one of the Chinese constellations. In Hindu astronomy, Spica corresponds to the Nakshatra Chitra.
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 the brightest of the rotating ellipsoidal variables. Its apparent magnitude varies between +0.92 and +1.04, with a period of 4.0142 days. This slight dip in magnitude is barely noticeable visually. It is also a variable of the Beta Cephei type.
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 ("follow the arc to Arcturus and speed on to Spica").
In medieval astrology, it was a Behenian fixed star, associated with the emerald and sage. In his De Occulta Philosophia, Cornelius Agrippa attributes its kabbalistic symbol 
to Hermes Trismegistus.
[edit] External links
- Spika, the first Slovene astronomical magazine, edited by Bojan Kambič and published since 1995 (Slovene)
- Astrospica, an astronomical image gallery named for Spica. (Spanish)
- Tables of past and future eclipses of bright stars by the inner planets. (German).
- [1] Eclipses of bright stars by planets, 3000 BC to 3000 AD.(Spanish)
- Bright Star Catalogue
