Canopus (Alpha Carinae)
Coordinates, Hipparcos distance (310 ly), magnitude −0.74, 71 R☉ yellow-white supergiant radius, and observing guide for Canopus in Carina.
Provenance-Backed Scientific Measurements
Every measurement below preserves its unit, uncertainty interval, observational method, reference epoch, quality status, and primary catalog source. See Uncertainty & Provenance for how competing measurements are handled.
| Parameter | Value | Uncertainty | Method & Epoch | Quality Status | Source Archive |
|---|---|---|---|---|---|
| Apparent visual magnitude (V) | -0.74 mag | ± 0.01 mag | Johnson UBV photoelectric photometry | definitive | Hipparcos New Reduction Catalog |
| Trigonometric parallax | 10.55 mas | ± 0.56 mas | Hipparcos New Reduction astrometric solution (94.8 ± 5.0 pc) (J2000.0) | definitive | Hipparcos New Reduction Catalog |
| Distance in light-years | 309.2 ly | ± 16.4 ly | Derived from Hipparcos parallax 10.55 ± 0.56 mas | high-confidence | Hipparcos New Reduction Catalog |
| Photospheric linear radius | 71.4 R☉ | ± 4 R☉ | VLTI/AMBER limb-darkened angular diameter (6.93 ± 0.15 mas) at 94.8 pc | high-confidence | SIMBAD Astronomical Database (CDS) |
| Bolometric luminosity | 10700 L☉ | ± 1100 L☉ | Integrated bolometric flux and Hipparcos distance modulus | high-confidence | SIMBAD Astronomical Database (CDS) |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Canopus (Alpha Carinae Bright Supergiant) at RA 06h 23m 57.11s, Dec -52° 41′ 44.4″ within Carina, alongside peak meridian transit altitudes for 40°N and 30°S observers. Use the RA/Dec Coordinate Converter to compute exact culmination altitude for your latitude.
Astrophysical Context & Structure
Canopus (Alpha Carinae) is the second-brightest star in Earth's night sky at apparent visual magnitude −0.74, outshone only by Sirius. Situated 94.8 ± 5.0 parsecs (309 light-years) away in the southern keel of Argo Navis (Carina), Canopus owes its brilliance to tremendous intrinsic power: within 700 light-years of the Solar System, it has the highest absolute visual magnitude (M_V = −5.71) of any star, radiating 10,700 times the bolometric output of the Sun.
Long-baseline optical interferometry with the Very Large Telescope Interferometer (VLTI) resolved Canopus's limb-darkened disk at 6.93 milliarcseconds, corresponding to a physical radius of 71.4 solar radii—if placed at the center of our Solar System, its photosphere would extend 90% of the way to the orbit of Mercury. Having exhausted its core hydrogen, this 8-to-9 solar-mass intermediate-mass star is currently executing a 'blue loop' across the Hertzsprung-Russell diagram while fusing helium in its core at an effective surface temperature of 7,400 K.
Because Canopus sits far from the ecliptic plane (ecliptic latitude −75.8°) where sunlight and zodiacal dust never interfere, and shines as an unmistakable zero-magnitude beacon, spacecraft since Mariner 4 in 1964 have used dedicated 'Canopus Star Trackers' to lock their roll attitude during interplanetary voyages across the Solar System.
Practical Visual Observing Guide
- Located 36° south of Sirius at declination −52°42′, Canopus is invisible north of +37°N latitude, but skims the southern winter horizon from the southern United States (Florida, Texas, Arizona, southern California) and the Mediterranean.
- From the Southern Hemisphere, Canopus rides high overhead on January and February nights, shining with a pure creamy-white luster free of the fierce atmospheric scintillation that affects low-altitude northern views.
Catalog Cross-Identifications & Aliases
Common Aliases: α Carinae · Suhel · HD 45348 · HIP 30438
| Catalog Authority | Identifier |
|---|---|
| HIP | HIP 30438 |
| HD | HD 45348 |
| SIMBAD | * alf Car |
| WIKIDATA | Q12189 |
Related Objects, Comparisons & Guides
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.
Miaplacidus (Beta Carinae Southern Subgiant)
Coordinates, Hipparcos distance (113.2 ly), magnitude 1.67, Diamond Cross asterism anchor, and observing guide for Miaplacidus in Carina.
Achernar (Alpha Eridani Oblate Be Star)
Coordinates, Hipparcos distance (139 ly), magnitude 0.46, extreme 1.35:1 equatorial flattening, and observing guide for Achernar in Eridanus.
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.
Scientific Sources & Dataset Provenance
- 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