Rigel vs Spica Blue Star Comparison
Compare blue supergiant Rigel (Beta Orionis, B8 Ia) and close binary blue giant Spica (Alpha Virginis, B1 III-IV) in UV temperature and luminosity.
Compared Celestial Objects
Rigel (Beta Orionis Blue Supergiant)
Coordinates, Hipparcos distance (264 pc), luminosity (120,000 L☉), Rigel BC companion, and observing guide for Rigel in Orion.
Constellation: Orion · Coords: 05h 14m 32.27s, -08° 12′ 05.9″
Spica (Alpha Virginis Ellipsoidal Binary)
Coordinates, Hipparcos distance (250 ly), 4.01-day close B-star binary, precession discovery history, and observing guide for Spica.
Constellation: Virgo · Coords: 13h 25m 11.58s, -11° 09′ 40.8″
Normalized Shared Parameter Table
| Parameter | Unit / Scale | Rigel (Beta Orionis Blue Supergiant) | Spica (Alpha Virginis Ellipsoidal Binary) |
|---|---|---|---|
| Apparent Visual Magnitude (V) | mag | +0.13 ± 0.03 | +0.97 ± 0.02 (ellipsoidal var) |
| Heliocentric Distance | pc | 264 ± 24 pc (860 ly) | 76.6 ± 3.9 pc (250 ly) |
| Effective Temperature (Teff) | K | 12,100 ± 150 K (B8 Ia) | 25,300 ± 500 K (B1 III-IV) |
| Bolometric Luminosity | L☉ | (1.20 ± 0.15) × 10⁵ L☉ | (2.05 ± 0.20) × 10⁴ L☉ (primary) |
| Photospheric Radius | R☉ | 78.9 ± 7.4 R☉ | 7.47 ± 0.50 R☉ (primary) |
Astrophysical & Observational Synthesis
Although both stars appear icy blue-white to the eye, Spica's primary component (B1 III-IV) has an effective surface temperature of 25,300 K—more than twice as hot as Rigel (12,100 K, B8 Ia). Because a 25,300 K blackbody radiates the vast majority of its photons in the far ultraviolet (requiring a bolometric correction of BC ≈ −2.6 mag), Spica's 7.5-solar-radius primary shines with 20,500 solar luminosities while appearing at V = +0.97 from 76.6 parsecs.
Rigel, despite sitting 3.4 times farther away in the Orion OB1 association (264 pc), outshines Spica by 0.84 magnitudes in visual light because Rigel is an evolved ~21 M☉ supergiant that has expanded to 78.9 solar radii (~10.5 times Spica's diameter), boosting its visual luminosity and radiating 120,000 L☉.
Their multiplicity also diverges across scales: Spica is an ultra-close 4.0145-day double-lined spectroscopic binary (11.4 M☉ + 7.2 M☉ separated by just 0.12 AU) whose mutually distorted egg-shaped stars cause a 0.03-mag ellipsoidal variation, whereas Rigel can be visually split in a 70 mm+ telescope from its 9.5-arcsecond companion Rigel BC (~2,500 AU away).
Related Reference Guides
Stellar Spectral Classification (OBAFGKM)
Reference guide to Morgan-Keenan (MK) stellar classification (O B A F G K M), luminosity classes (I–V, WD), color index (B-V), and the H-R diagram.
Apparent vs Absolute Magnitude Explained
Understand the logarithmic Pogson astronomical magnitude scale, apparent visual magnitude (m), absolute magnitude (M at 10 parsecs), and bolometric corrections.
Primary Catalogs & Scientific Sources
- ESA Gaia Archive — Data Release 3 (DR3 (2022-06-13)): Gaia Collaboration, Vallenari, A., et al. 2023, A&A, 674, A1 (Gaia Data Release 3) — European Space Agency / Gaia DPAC
- SIMBAD Astronomical Database (CDS) (2026-10 release): Wenger, M., et al. 2000, A&AS, 143, 9 (The SIMBAD astronomical database) — Centre de Données astronomiques de Strasbourg
- Revised New General Catalogue and Index Catalogue (RNGC/IC) (2024/2026 edition): Steinicke, W. 2010, Observing and Cataloguing Nebulae and Star Clusters (Cambridge Univ. Press); Verga, M. OpenNGC (CC-BY-SA 4.0 / data tables) — Wolfgang Steinicke / OpenNGC