  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Orion |
| Right ascension | 04h 49m 50.41091s[1] |
| Declination | +06° 57′ 40.5883″[1] |
| Apparent magnitude (V) | 3.16[2] |
| Characteristics | |
| Spectral type | F6 V[2] |
| U−Bcolor index | +0.00[2] |
| B−Vcolor index | +0.46[2] |
| Variable type | Suspected[3] |
| Astrometry | |
| Radial velocity (Rv) | 24.1[4] km/s |
| Proper motion (μ) | RA: 464.06[1]mas/yr Dec.: 11.21[1]mas/yr |
| Parallax (π) | 123.94±0.17 mas[1] |
| Distance | 26.32 ± 0.04 ly (8.07 ± 0.01 pc) |
| Absolute magnitude (MV) | 3.65[5] |
| Details[6] | |
| Mass | 1.288±0.019 M☉ |
| Radius | 1.317±0.004 R☉ |
| Luminosity | 2.816±0.06 L☉ |
| Surface gravity (log g) | 4.31±0.01 cgs |
| Temperature | 6,518±35 K |
| Metallicity[Fe/H] | 0.03±0.03 dex |
| Rotational velocity (v sin i) | 17[7] km/s |
| Age | 1.04[8] Gyr |
| Other designations | |
| Tabit,π3 Ori,1 Ori,BD+06°762,FK5 1134,GCTP 1077.00,Gliese 178,HD 30652,HIP 22449,HR 1543,LTT 11517,SAO 112106[9] | |
| Database references | |
| SIMBAD | data |
Pi3 Orionis (π3 Orionis, abbreviatedPi3 Ori,π3 Ori), also namedTabit/ˈteɪbɪt/,[10][11] is astar in theequatorialconstellation ofOrion. At anapparent visual magnitude of 3.16,[2] it isreadily visible to the naked eye and is the brightest and nearest star in the lion's hide (or shield) that Orion is holding. As measured using theparallax technique, it is 26.32light-years (8.07parsecs) distant from theSun.[1]
π3 Orionis (Latinised toPi3 Orionis) is the system'sBayer designation.
It bore the traditional name of 'Tabit', from theArabic الثابتal-thābit 'the endurer (the fixed/constant one)'.[12] In 2016, the IAU organized aWorking Group on Star Names (WGSN)[13] to catalog and standardize proper names for stars. The WGSN approved the nameTabit for this star on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.[11]
InChinese,參旗 (Sān Qí), meaningBanner of Three Stars, refers to anasterism consisting of π3 Orionis,ο1 Orionis,ο2 Orionis,6 Orionis,π1 Orionis,π2 Orionis,π4 Orionis,π5 Orionis andπ6 Orionis.[14] Consequently, theChinese name for Pi3 Orionis itself is參旗六 (Zhāng Qí Liù), "the Sixth Star of Banner of Three Stars".[15]
According toRichard Hinckley Allen: Star Names – Their Lore and Meaning, this star, together with ο1 Orionis, ο2 Orionis, π1 Orionis, π2 Orionis, π4 Orionis, π5 Orionis, π6 Orionis and 6 Orionis (are all of the 4th to the 5th magnitudes and in a vertical line), indicate the lion's skinwere but Al Tizini said that they were the Persians'Al Tāj, "the Crown", or "Tiara", of their kings; and the Arabians'Al Kumm, "the Sleeve", of the garment in which they dressed the Giant, the skin being omitted.Ulugh Beg called themAl Dhawāib, "Anything Pendent"; and theBorgian globe had the same, perhaps originated it.Al Sufi's title wasManica, a Latin term for a protecting Gauntlet; andGrotius gave a lengthy dissertation on theMantile, which some anonymous person applied to them, figured as a cloth thrown over the Giant's arm.[16]
Pi3 Orionis is most likely single; a nearby star is probably an optical companion.[17]
It is amain-sequence star ofspectral type F6 V. Since 1943, thespectrum of this star has served as one of the stable anchor points by which other stars are classified.[18] Compared to the Sun, it has about 129% of themass, 132% of theradius, and nearly 3 times theluminosity. This energy is being radiated from the star'souter atmosphere at aneffective temperature of6,518 K,[6] giving it the yellow-white glow of anF-type star.
Although a periodicity of 73.26 days has been observed in the star's radial velocity, it seems likely to be bound more to stellar activity than to aplanetary object in closeorbit. Nosubstellar companion has been detected so far around Tabit and theMcDonald Observatory team has set limits to the presence of one or more planets[19] with masses between 0.84 and 46.7Jupiter masses and average separations spanning between 0.05 and 5.2astronomical units. Thus, so far it appears that planets could easily orbit in thehabitable zone without any complications caused by agravitationally perturbing body.
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