Zeta Centauri
Star in the constellation Centaurus
From Wikipedia, the free encyclopedia
Zeta Centauri is a binary star system in the southern constellation of Centaurus. It has the proper name Leepwal;[11] Zeta Centauri is its Bayer designation. With a combined apparent visual magnitude of +2.55,[2] it is one of the brighter members of the constellation. This system is close enough to the Earth that its distance can be measured directly using the parallax technique. This yields a value of roughly 382 light-years (117 parsecs), with a 1.6% margin of error.[1] It is drifting further away with a radial velocity of +6.5 km/s.[4]
 | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Centaurus |
| Right ascension | 13h 55m 32.38565s[1] |
| Declination | −47° 17′ 18.1482″[1] |
| Apparent magnitude (V) | +2.55[2] |
| Characteristics | |
| Spectral type | B2.5 IV[3] |
| U−B color index | −0.91[2] |
| B−V color index | −0.22[2] |
| Astrometry | |
| Radial velocity (Rv) | +6.5[4] km/s |
| Proper motion (μ) | RA: −57.37[1] mas/yr Dec.: −44.55[1] mas/yr |
| Parallax (π) | 8.54±0.13 mas[1] |
| Distance | 382 ± 6 ly (117 ± 2 pc) |
| Absolute magnitude (MV) | −2.79[5] |
| Orbit[6] | |
| Period (P) | 8.024 days |
| Semi-major axis (a) | 0.0014"[7] |
| Eccentricity (e) | 0.5 |
| Periastron epoch (T) | 2413719.321 JD |
| Argument of periastron (ω) (secondary) | 290° |
| Details | |
| Mass | 7.8±0.1[3] M☉ |
| Radius | 5.80±0.53[8] R☉ |
| Luminosity | 5,884[5] L☉ |
| Surface gravity (log g) | 3.84±0.08[8] cgs |
| Temperature | 23561±283[8] K |
| Rotational velocity (v sin i) | 235[9] km/s |
| Age | 39.8±5.7[3] Myr |
| Other designations | |
| Leepwal, ζ Cen, CD−46 8949, CPD−46 6560, HD 121263, HIP 68002, HR 5231, SAO 224538[10] | |
| Database references | |
| SIMBAD | data |
ζ Cen is a double-lined spectroscopic binary system,[12] which indicates that the orbital motion was detected by shifts in the absorption lines of their combined spectra caused by the Doppler effect. The two stars orbit each other over a period of slightly more than eight days with an orbital eccentricity of about 0.5.[6] The estimated angular separation of the pair is 1.4 mas.[7]
At an estimated age of 40 million years,[3] the primary component of this system appears to be in the subgiant stage of its evolution with a stellar classification of B2.5 IV.[3] It is a large star with nearly 8[3] times the mass of the Sun and close to 6[8] times the Sun's radius. This star is rotating rapidly with a projected rotational velocity of 235 km s−1.[9]
Nomenclature
Zeta Centauri, Latinized from ζ Centauri, is the star's Bayer designation. Along with other modern Bayer designations in Centaurus, it was assigned by Nicolas Louis de Lacaille in his 1756 star catalog; the star referred to as ζ Centauri in Bayer's Uranometria of 1603 is Acrux in the Southern Cross, then considered part of Centaurus.[13]
This star has been referred to by the proper name Alnair /æˈnɛər/, from Arabic: نير بطن قنطورس, romanized: nayyir baṭan qanṭūris, lit. 'the bright (star) of the body of the centaur',[14][15] though this was originally a name for Acrux (see above).[16][13] Alnair is also the proper name of α Gruis and was officially approved by the IAU as the name of that star.[11] This star has also been referred to as Baten Kentaurus, from the same Arabic source.[17]
In Chinese, 庫樓 (Kù Lóu), meaning Arsenal, refers to an asterism consisting of ζ Centauri, η Centauri, θ Centauri, 2 Centauri, HD 117440, ξ1 Centauri, γ Centauri, τ Centauri, D Centauri and σ Centauri.[18] Consequently, the Chinese name for ζ Centauri itself is 庫樓一 (Kù Lóu yī, English: the First Star of Arsenal.)[19] (See also ι Centauri.)
In Marshallese, this star is named Ļeepwal (pronounced leyepwal), the third of the ten sons of Lōktañūr (Capella).[20] The IAU Working Group on Star Names approved the name Leepwal for Zeta Centauri A on 18 July 2024 and it is now so entered in the IAU Catalog of Star Names.[11]