Sirius A & B vs Vega A-Star Comparison
Compare the Sirius A/B binary system (A1 V main-sequence star + DA2 white dwarf at 2.64 pc) against zero-point A0 V standard Vega (at 7.68 pc).
Compared Celestial Objects
Sirius (Alpha Canis Majoris Binary)
Coordinates, Hipparcos parallax (379.21 mas, 8.60 ly), magnitude −1.46, Sirius B white dwarf orbit, and observing guide for Sirius.
Constellation: Canis Major · Coords: 06h 45m 08.92s, -16° 42′ 58.0″
Vega (Alpha Lyrae Zero-Point Star)
Coordinates, distance (25.04 ly), magnitude 0.03 photometric zero point, rapid oblate rotation, and observing guide for Vega in Lyra.
Constellation: Lyra · Coords: 18h 36m 56.34s, +38° 47′ 01.3″
Normalized Shared Parameter Table
| Parameter | Unit / Scale | Sirius (Alpha Canis Majoris Binary) | Vega (Alpha Lyrae Zero-Point Star) |
|---|---|---|---|
| Apparent Visual Magnitude (V) | mag | −1.460 ± 0.010 (Sirius B: +8.44) | +0.026 ± 0.008 |
| Heliocentric Distance | pc | 2.637 ± 0.001 pc (8.60 ly) | 7.678 ± 0.008 pc (25.04 ly) |
| Bolometric Luminosity | L☉ | 25.4 ± 0.5 L☉ (Sirius B: 0.056 L☉) | 40.12 ± 0.45 L☉ |
| Stellar Mass | M☉ | 2.063 M☉ (Sirius B: 1.018 M☉) | 2.135 ± 0.074 M☉ |
| Effective Temperature (Teff) | K | 9,940 K (Sirius B: 25,200 K) | 9,602 ± 180 K (A0 Va) |
Astrophysical & Observational Synthesis
Sirius A and Vega are nearly twin 2.1 M☉ A-type main-sequence stars, yet Vega is 58% more luminous (40.1 L☉ vs 25.4 L☉) because Vega is more evolved (~455 Myr vs ~242 Myr) and viewed pole-on above a rapidly rotating equator; Sirius outshines Vega by 1.49 magnitudes solely because Sirius sits 2.91 times closer to Earth (2.64 pc vs 7.68 pc), boosting its apparent visual flux by a factor of 8.5.
Even more striking is the internal contrast within the Sirius binary itself: degenerate carbon-oxygen white dwarf Sirius B has an effective temperature of 25,200 K—more than twice as hot as Sirius A and Vega—and packs 1.018 solar masses inside an Earth-sized radius (0.0084 R☉), making it 10,000 times fainter in visual light (+8.44 vs −1.46) across an 11-arcsecond orbital separation.
Related Reference Guides
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.
Trigonometric Parallax, Parsecs & Gaia DR3
How trigonometric parallax (d_pc = 1 / p_arcsec), the distance modulus equation, Hipparcos, and Gaia DR3 microarcsecond astrometry measure cosmic distances.
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.
Primary Catalogs & Scientific Sources
- Hipparcos New Reduction Catalog (2007 New Reduction): van Leeuwen, F. 2007, A&A, 474, 653 (Validation of the new Hipparcos reduction) — ESA / van Leeuwen (2007)
- 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