Miaplacidus (Beta Carinae)
Coordinates, Hipparcos distance (113.2 ly), magnitude 1.67, Diamond Cross asterism anchor, and observing guide for Miaplacidus 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) | 1.67 mag | ± 0.01 mag | Johnson UBV photoelectric photometry | definitive | Hipparcos New Reduction Catalog |
| Trigonometric parallax | 28.82 mas | ± 0.32 mas | Hipparcos New Reduction astrometric solution (34.70 ± 0.39 pc) (J2000.0) | definitive | Hipparcos New Reduction Catalog |
| Distance in light-years | 113.2 ly | ± 1.3 ly | Derived from Hipparcos parallax 28.82 ± 0.32 mas | definitive | Hipparcos New Reduction Catalog |
| Photospheric radius | 6.8 R☉ | ± 0.3 R☉ | Narrabri intensity interferometry angular diameter (1.59 ± 0.07 mas) at 34.70 pc | high-confidence | SIMBAD Astronomical Database (CDS) |
| Bolometric luminosity | 288 L☉ | ± 15 L☉ | Integrated spectrophotometry + Hipparcos parallax | definitive | SIMBAD Astronomical Database (CDS) |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Miaplacidus (Beta Carinae Southern Subgiant) at RA 09h 13m 11.98s, Dec -69° 43′ 01.9″ 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
Miaplacidus (Beta Carinae) is the second-brightest star in Carina after Canopus and the twenty-eighth brightest star in the entire night sky at apparent visual magnitude 1.67.Lying at declination −69° 43′—farther south than Acrux, Alpha Centauri, or Canopus—Miaplacidus is the brightest star in the deep far-southern sky within 20 degrees of the South Celestial Pole. Its Bilingual name, coined by Welsh cartographer Elijah Hinsdale Burritt in his 1856 Geography of the Heavens, blends the Arabic word miyāh ('waters') with the Latin placidus ('calm' or 'placid').
Located 34.70 ± 0.39 parsecs (113.2 light-years) from Earth, Miaplacidus is a ~3.5-solar-mass, ~260-million-year-old A1 III / A2 IV star that has exhausted its core hydrogen and swollen to 6.8 solar radii. Radiating 288 times the Sun's luminosity from an 8,866 K photosphere, it is caught in the rapid evolutionary transition between a main-sequence A-dwarf and a cool red giant.
In southern sky lore and navigation, Miaplacidus anchors the southwestern vertex of the 'Diamond Cross'—a prominent four-star asterism formed with Theta Carinae (in the Southern Pleiades cluster IC 2602), Upsilon Carinae, and Omega Carinae, sitting directly adjacent to the False Cross and the true Southern Cross (Crux).
Practical Visual Observing Guide
- At declination −69°43′, Miaplacidus never rises north of +20°N latitude and is circumpolar for all observers south of −20°S (including Sydney, Melbourne, Auckland, Buenos Aires, Santiago, and Cape Town).
- Just 4.8° north-northwest of Miaplacidus lies the globular cluster NGC 2808, one of the most massive and concentrated globular clusters in the Milky Way (magnitude 6.2), easily spotted in binoculars.
Catalog Cross-Identifications & Aliases
Common Aliases: β Carinae · HD 80007 · HIP 45238
| Catalog Authority | Identifier |
|---|---|
| HIP | HIP 45238 |
| HD | HD 80007 |
| SIMBAD | * bet Car |
| WIKIDATA | Q13045 |
Related Objects, Comparisons & Guides
Canopus (Alpha Carinae Bright Supergiant)
Coordinates, Hipparcos distance (310 ly), magnitude −0.74, 71 R☉ yellow-white supergiant radius, and observing guide for Canopus in Carina.
Acrux (Alpha Crucis Southern Cross Multiple)
Coordinates, Hipparcos distance (321 ly), magnitude 0.76, 4.0″ B-star visual binary + α Cru C triple, and observing guide for Acrux.
Eta Carinae (Luminous Blue Variable Binary)
Coordinates, Gaia/expansion distance (2.35 kpc), 5 million L☉ luminosity, 1843 Great Eruption Homunculus, and observing guide for Eta Carinae.
Celestial Coordinates (RA & Dec) Explained
Practical reference to J2000 equatorial coordinates: Right Ascension (RA in hours, minutes, seconds), Declination (Dec in degrees), and sexagesimal conversion.
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