Spica
Spica is the brightest object in the constellation of Virgo and one of the 20 brightest stars in the night sky. It has the Bayer designation α Virginis, which is Latinised to Alpha Virginis and abbreviated Alpha Vir or α Vir. Analysis of its parallax shows that it is located 250±10 light-years from the Sun. It is a spectroscopic binary star and rotating ellipsoidal variable; a system whose two stars are so close together they are egg-shaped rather than spherical, and can only be separated by their spectra. The primary is a blue giant and a variable star of the Beta Cephei type.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Virgo |
| Pronunciation | /ˈspaɪkə/ or /ˈspiːkə/ |
| Right ascension | 13h 25m 11.579s |
| Declination | −11° 09′ 40.75″ |
| Apparent magnitude (V) | +0.97 (0.97–1.04) |
| Characteristics | |
| Spectral type | B1V (B1III-IV + B2V) |
| U−B color index | −0.94 |
| B−V color index | −0.23 |
| Variable type | β Cep + Ellipsoidal |
| Astrometry | |
| Radial velocity (Rv) | +1.0 km/s |
| Proper motion (μ) | RA: −42.35±0.62 mas/yr Dec.: −30.67±0.37 mas/yr |
| Parallax (π) | 13.06 ± 0.70 mas |
| Distance | 250 ± 10 ly (77 ± 4 pc) |
| Absolute magnitude (MV) | −3.55 (−3.5/−1.5) |
| Orbit | |
| Period (P) | 4.0145±0.0001 d |
| Semi-major axis (a) | 28.20±0.92 R☉ |
| Eccentricity (e) | 0.133±0.017 |
| Inclination (i) | 63.1±2.5° |
| Periastron epoch (T) | 2,454,189.4±0.02 |
| Argument of periastron (ω) (secondary) | 255.6±12.2° |
| Details | |
| Primary | |
| Mass | 11.43±1.15 M☉ |
| Radius | 7.47±0.54 R☉ |
| Luminosity | 20,512+5,015 −4,030 L☉ |
| Surface gravity (log g) | 3.71±0.10 cgs |
| Temperature | 25,300±500 K |
| Rotational velocity (v sin i) | 165.3±4.5 km/s |
| Age | 12.5 Myr |
| Secondary | |
| Mass | 7.21±0.75 M☉ |
| Radius | 3.74±0.53 R☉ |
| Luminosity | 2,254+1,166 −768 L☉ |
| Surface gravity (log g) | 4.15±0.15 cgs |
| Temperature | 20,900±800 K |
| Rotational velocity (v sin i) | 58.8±1.5 km/s |
| Other designations | |
Spica, Azimech, Spica Virginis, α Virginis, Alpha Vir, 67 Virginis, BD−10°3672, FK5 498, HD 116658, HIP 65474, HR 5056, SAO 157923, CCDM 13252-1109 | |
| Database references | |
| SIMBAD | data |
Spica, along with Arcturus and Denebola—or Regulus, depending on the source—forms the Spring Triangle asterism, and, by extension, is also part of the Great Diamond together with the star Cor Caroli.