Mintaka (Delta Orionis)
Coordinates, distance (~1,200 ly), magnitude 2.23, 5.73-day O-star eclipsing binary, interstellar Ca II discovery, and guide for Mintaka.
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 |
|---|---|---|---|---|---|
| Combined apparent visual magnitude (V) | 2.23 mag | ± 0.06 mag | Photoelectric V-band photometry (eclipses between 2.20 and 2.32 mag) | definitive | Hipparcos New Reduction Catalog |
| Distance (Orion OB1b / Gaia DR3 companion) | 380 pc | ± 30 pc | Eclipsing binary spectrophotometry & companion HD 36485 Gaia DR3 parallax (~1,240 ly; Hipparcos = 212 ± 30 pc) | high-confidence | ESA Gaia Archive — Data Release 3 |
| Inner eclipsing binary orbital period (Aa1–Aa2) | 5.732436 d | ± 0.000015 d | MOST & Coriolis space photometry + radial velocity | definitive | SIMBAD Astronomical Database (CDS) |
| Primary O9.5 II star mass (Mintaka Aa1) | 24 M☉ | ± 3 M☉ | Eclipsing binary dynamical modeling (Shenar et al. 2015; companion Aa2 = 8.4 ± 1.0 M☉) | high-confidence | SIMBAD Astronomical Database (CDS) |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Mintaka (Delta Orionis Eclipsing Multiple) at RA 05h 32m 00.40s, Dec -00° 17′ 56.7″ within Orion, 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
Mintaka (Delta Orionis, from the Arabic al-Minṭaqah meaning 'the Belt') marks the western (right-hand) end of Orion's Belt, shining at apparent visual magnitude 2.23. Situated just 17.9 arcminutes (0.30°) south of the celestial equator (declination −00° 17′ 57″), Mintaka rises almost due east and sets almost due west from every inhabited latitude on Earth, making it a universal celestial compass.
In 1904 German astronomer Johannes Hartmann observed the 5.732-day spectroscopic binary orbit of Mintaka and noticed something extraordinary: while the helium and hydrogen spectral lines of the orbiting O9.5 II giant and B1 V companion shifted back and forth by >200 km/s every 5.73 days, the narrow ionized calcium (Ca II H and K) absorption lines remained completely stationary! That landmark observation proved for the first time that space between the stars is not an empty vacuum, discovering the interstellar medium.
Located ~380 parsecs (1,240 light-years) away, the Mintaka complex contains at least five massive stars: the 5.73-day eclipsing pair (Aa1 and Aa2, radiating ~190,000 solar luminosities at 29,500 K), a close B0 IV interferometric companion (Mintaka Ab) orbiting every ~346 years, and a wide 6.85-magnitude B2 V spectroscopic binary companion (Mintaka C / HD 36485) sitting 52.6 arcseconds directly north.
Practical Visual Observing Guide
- Mintaka is one of the easiest and most rewarding double stars in the winter sky: any 40–60 mm telescope at 25×–50× (or steadily braced 10×50 binoculars) cleanly splits 2.23-magnitude Mintaka A from its 6.85-magnitude blue-white companion Mintaka C (HD 36485) 52.6 arcseconds to the north.
- Because Mintaka lies almost dead on the celestial equator, turning off your telescope's clock drive and timing how long Mintaka takes to drift across your eyepiece field of view yields your exact true field of view (at 15.04 arcseconds per second of time).
Catalog Cross-Identifications & Aliases
Common Aliases: δ Orionis · HD 36486 · HIP 25930 · 34 Orionis
| Catalog Authority | Identifier |
|---|---|
| HIP | HIP 25930 |
| HD | HD 36486 |
| SIMBAD | * del Ori |
| WIKIDATA | Q13037 |
Related Objects, Comparisons & Guides
Alnilam (Epsilon Orionis Belt Supergiant)
Coordinates, distance (~1,340–2,000 ly), magnitude 1.69, 837,000 L☉ blue supergiant luminosity, and observing guide for Alnilam in Orion.
Alnitak (Zeta Orionis O-Type Supergiant)
Coordinates, distance (~1,260 ly), magnitude 1.77, brightest O-type star in the sky, triple system, and observing guide for Alnitak.
Bellatrix (Gamma Orionis Blue Giant Star)
Coordinates, Hipparcos distance (252 ly), magnitude 1.64, B2 III spectral standard, and observing guide for Bellatrix in Orion.
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.
Proper Motion, Radial Velocity & Redshift
How astronomers combine tangential proper motion (mas/yr), Doppler radial velocity (km/s), and cosmological redshift (z) to reconstruct 3D space motion.
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