Mintaka/ˈmɪntəkə/,[17] designationDelta Orionis (δ Orionis, abbreviatedDelta Ori,δ Ori) and34 Orionis (34 Ori), is a multiplestar system some 1,200light-years from theSun in theconstellation ofOrion. Together withAlnitak (Zeta Orionis) andAlnilam (Epsilon Orionis), the three stars formOrion's Belt, known by many names among ancient cultures. The star is located very close to thecelestial equator. When Orion is near themeridian, Mintaka is the rightmost of the Belt's stars when viewed from theNorthern Hemisphere facingsouth.
 Orion's Belt (composed of the three brightest stars shown), Mintaka being the rightmost, on the west side | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Orion |
| δ Ori A (Aa1 + Aa2 + Ab) | |
| Right ascension | 05h 32m 00.40009s[1] |
| Declination | −00° 17′ 56.7424″[1] |
| Apparent magnitude (V) | 2.23[2](2.50 + 3.90[3]) |
| δ Ori B | |
| Right ascension | 05h 31m 58.745s[4] |
| Declination | −00° 18′ 18.65″[4] |
| Apparent magnitude (V) | 14.0[5] |
| HD 36485 | |
| Right ascension | 05h 32m 00.406s[6] |
| Declination | −00° 17′ 04.38″[6] |
| Apparent magnitude (V) | 6.85[5] |
| Characteristics | |
| A | |
| Spectral type | O9.5II + B1V +B0IV[7] |
| U−Bcolor index | −1.05[2] |
| B−Vcolor index | −0.22[2] |
| Variable type | Eclipsing binary[8] |
| HD 36485 | |
| Spectral type | B3V + A0V[9] |
| U−Bcolor index | −0.71[10] |
| B−Vcolor index | −0.16[10] |
| Astrometry | |
| Radial velocity (Rv) | 18.50±0.5[11] km/s |
| Proper motion (μ) | RA: 0.64±0.56[1]mas/yr Dec.: −0.69±0.27[1]mas/yr |
| Parallax (π) | 4.71±0.58 mas[1] |
| Distance | 1,200[7] ly (380[7] pc) |
| Absolute magnitude (MV) | −5.8[5] |
| δ Ori Aa1 | |
| Absolute magnitude (MV) | −5.4[5] |
| δ Ori Aa2 | |
| Absolute magnitude (MV) | −2.9[5] |
| δ Ori Ab | |
| Absolute magnitude (MV) | −4.2[5] |
| HD 36485 | |
| Proper motion (μ) | RA: +1.523[12]mas/yr Dec.: −1.653[12]mas/yr |
| Parallax (π) | 2.6245±0.0538 mas[12] |
| Distance | 1,240 ± 30 ly (381 ± 8 pc) |
| Orbit[13] | |
| Primary | δ Ori Aa1 |
| Companion | δ Ori Aa2 |
| Period (P) | 5.732436 days |
| Semi-major axis (a) | 43.1±1.7 R☉ |
| Eccentricity (e) | 0.1133±0.0003 |
| Inclination (i) | 76.5±0.2° |
| Periastronepoch (T) | 2,456,295.674±0.062 |
| Argument of periastron (ω) (secondary) | 141.3±0.2° |
| Orbit[9] | |
| Primary | δ Ori Aa1/2 |
| Companion | δ Ori Ab |
| Period (P) | 53,839 days |
| Semi-major axis (a) | 20,038 R☉ |
| Eccentricity (e) | 0.5886±0.016 |
| Inclination (i) | 104.7±0.4° |
| Longitude of the node (Ω) | 122.4±0.5° |
| Periastronepoch (T) | 2,458,773.2±0.1 |
| Argument of periastron (ω) (secondary) | 259±2° |
| Details | |
| δ Ori Aa1 | |
| Mass | 17.8[9] M☉ |
| Radius | 13.1[9] R☉ |
| Luminosity | 190,000[7] L☉ |
| Surface gravity (log g) | 3.55±0.05[9] cgs |
| Temperature | 31,400±1,000[9] K |
| Rotational velocity (v sin i) | 114±20[9] km/s |
| δ Ori Aa2 | |
| Mass | 8.518[9] M☉ |
| Radius | 4.168[9] R☉ |
| Luminosity | 16,000[7] L☉ |
| Surface gravity (log g) | 3.48±0.06[9] cgs |
| Temperature | 25,442±1,500[9] K |
| Rotational velocity (v sin i) | 89±15[9] km/s |
| δ Ori Ab | |
| Mass | 8.787[9] M☉ |
| Radius | 12.045[9] R☉ |
| Luminosity | 63,000[7] L☉ |
| Surface gravity (log g) | 3.64±0.05[9] cgs |
| Temperature | 30,250±1,000[9] K |
| Rotational velocity (v sin i) | 216±25[9] km/s |
| δ Ori B | |
| Radius | 0.77[14] R☉ |
| Luminosity | 0.431[14] L☉ |
| Temperature | 5,324[14] K |
| HD 36485 | |
| Mass | 6-11[15] M☉ |
| Radius | 5.7[16] R☉ |
| Luminosity | 3,300[16] L☉ |
| Surface gravity (log g) | 4.41[16] cgs |
| Temperature | 18,400[16] K |
| Other designations | |
| Mintaka,δ Orionis,34 Orionis, 88 G. Orionis,FK5 206,HIP 25930,ADS 4134,CCDM J05320-0018,WDS J05320-0018 | |
| Mintaka Aa:HD 36486,HR 1851,SAO 132220/132221,BD−00°983,GC 6847 | |
| Mintaka Ab:CCDM J05320-0018D,WDS J05320-0018Ab | |
| δ Ori B:UCAC3 180-24383,CCDM J05320-0018B,WDS J05320-0018B | |
| HD 36485:δ Orionis C,HR 1851,SAO 132221,BD−00°982,GC 6848,PLX 1261,CCDM J05320-0018C | |
| Database references | |
| SIMBAD | data |
| δ Ori B | |
| HD 36485 | |
Nomenclature
editDelta Orionis is the star'sBayer designation,34 Orionis itsFlamsteed designation. The nameMintaka itself is derived from anArabic term for 'belt': منطقة ormanṭaqa.[18] In 2016, theInternational Astronomical Union organized aWorking Group on Star Names (WGSN)[19] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[20] included a table of the first two batches of names approved by the WGSN, which includedMintaka for this star. It is now so entered in the IAU Catalog of Star Names.[21]
Observational history
edit
Mintaka is the westernmost of the three stars of Orion's belt. It is easily visible to the naked eye, one of thebrightest stars in the sky, and has been known since antiquity.
Radial velocity measurements taken byHenri-Alexandre Deslandres in 1900 atParis Observatory showed that Mintaka had a variable radial velocity and therefore was aspectroscopic binary.[22] His preliminaryorbital period estimate of 1.92 days was shown to be incorrect in 1904 whenJohannes Franz Hartmann using photographic plates taken atPotsdam Observatory showed that the orbital period was 5.7 days.[23] Hartmann also noticed that thecalcium K line at 393.4 nanometres in thestellar spectrum did not share in the periodic displacements of the lines due to orbital motion of the star and theorized that there was a cloud in the line of sight to Mintaka that containedcalcium. This was the first detection of theinterstellar medium.[23]
System
editδ Orionis is amultiple star system. There is amagnitude 7 star about 52arcseconds away from the second-magnitude primary and a much fainter star in between. The system is designated WDS 05320-0018 in theWashington Double Star Catalog, with the 14th-magnitude companion listed as component B and the seventh-magnitude star as component C.[24]
The primary component is itself a triple system: aclass-O9.5 bright giant and aclass-Bmain-sequence star orbit every 5.73 days and exhibit shallow eclipses when the star dims about 0.2 of a magnitude,[8] and a B-classsubgiant is resolved 0.26" away.[3] At the primary eclipse, the apparent magnitude (of the whole system) drops from 2.23 to 2.35, while it only drops to 2.29 at the secondary eclipse.[26]
The outer star of the triple system orbits the inner pair once every 53,839 days (147.40 yr). The orbit is quite eccentric, with the separation varying between 8,244solar radii (38.34 au) and 31,832 solar radii (148.03 au).[9]
The seventh-magnitude companion, HD 36485, is achemically peculiarB-type main-sequence star and itself a spectroscopic binary with a faint A-type companion in a 30-day orbit. It has an unusual spectrum withH-alphaemission and unusually strong heliumabsorption lines. It has a strong magnetic field and a very slow rotational velocity that produces chemical stratification in its atmosphere, which leads to the unusual abundances seen in the spectrum.[15]
The 14th-magnitude companion is thought to be around the same distance and is a somewhat cooler and less luminous star than the Sun.[14]
Mintaka is surrounded by a cluster of faint stars, possibly part of the cluster surroundingσ Ori.[27]
Distance
editThe distance derived from theHipparcos satellite parallax is212±30 parsecs,[1] while spectroscopic distances, comparisons to similar stars, and cluster membership all suggest a value more than double that.[13] This type of unreconcilable discrepancy is not unique to Mintaka and the reasons for it have yet to be clarified.[7] InGaia Data Release 3, component C is listed with a parallax of3.4531±0.0371 mas,[12] consistent with the distances derived by other methods but disagreeing with theHipparcos-derived value for the primary.[1]
The Gaia DR3 parallax for component B is3.5002″±0.0119″, strongly suggesting it is considerably closer than the other members of the system and merely a chance alignment.[28] At that distance it is likely to be aK-type main sequence star.[9]
Etymology and cultural significance
editMintaka was seen by astrologers as a portent of good fortune.[18]
Orion's Belt
edit
The three belt stars were collectively known by many names in many cultures. Arabic terms includeAl Nijād 'the Belt',Al Nasak 'the Line',Al Alkāt 'the Golden Grains or Nuts', and, in modern Arabic,Al Mīzān al Ḥakk 'the Accurate Scale Beam'. InChinese mythology, they were also known as the Weighing Beam.[citation needed]
InChinese,參宿 (Shēn Sù), meaningThree Stars (asterism), refers to an asterism consisting of Mintaka,Alnilam, andAlnitak (Orion's Belt), withBetelgeuse,Bellatrix,Saiph andRigel later added.[29] Consequently, theChinese name for Mintaka is參宿三 (Shēn Sù sān, English:the Third Star of Three Stars).[30] It is one of the western mansions of theWhite Tiger.
Namesakes
editTheUSSMintaka (AK-94) was aUnited States NavyCrater-class cargo ship named after the star.
References
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