  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquarius |
| Right ascension | 22h 16m 50.03635s[1] |
| Declination | –07° 46′ 59.8480″[1] |
| Apparent magnitude (V) | 4.175[2] |
| Characteristics | |
| Spectral type | G8 III–IV[3] |
| U−Bcolor index | +0.818[2] |
| B−Vcolor index | +0.983[2] |
| Astrometry | |
| Radial velocity (Rv) | –13.77 ± 0.17[4] km/s |
| Proper motion (μ) | RA: +118.80[1]mas/yr Dec.: –22.18[1]mas/yr |
| Parallax (π) | 17.40±0.23 mas[1] |
| Distance | 187 ± 2 ly (57.5 ± 0.8 pc) |
| Absolute magnitude (MV) | +0.23[3] |
| Details | |
| Mass | 2.39[5] to 2.78[3] M☉ |
| Radius | 12[4] R☉ |
| Luminosity | 72[4] to 83[3] L☉ |
| Surface gravity (log g) | 2.8[4] cgs |
| Temperature | 4,864[4] K |
| Metallicity [Fe/H] | +0.01[4] to +0.09[3] dex |
| Rotational velocity (v sin i) | 1.6[4] km/s |
| Age | 437[3] Myr |
| Other designations | |
| Ancha, 43 Aquarii,BD–08 5845,FK5 840,HD 211391,HIP 110003,HR 8499,SAO 145991.[6] | |
| Database references | |
| SIMBAD | data |
Theta Aquarii (θ Aquarii, abbreviatedTheta Aqr,θ Aqr), officially namedAncha/ˈæŋkə/[7] (distinguishAnkaa, with the same pronunciation), is astar in theequatorialconstellation ofAquarius. Visible to the naked eye atapparent magnitude 4.175,[2] it is located at a distance of around 187light-years (57parsecs) from theSun.[1] Since it is near theecliptic it can beocculted by theMoon, or very rarely byplanets.
θ Aquarii (Latinised toTheta Aquarii) is the star'sBayer designation.
It bore the traditional nameAncha;Medieval Latin for "thehaunch". In 2016, theInternational Astronomical Union organized aWorking Group on Star Names (WGSN)[8] to catalogue and standardize proper names for stars. The WGSN approved the nameAncha for this star on 12 September 2016, and it is now so included in the List of IAU-approved Star Names.[7]
InChinese,泣 (Qì), meaningWeeping, refers to anasterism consisting of Theta Aquarii andRho Aquarii.[9] Consequently, theChinese name for Theta Aquarii itself is泣二 (Qì èr, English:the Second Star of Weeping).[10] Possibly, the nameLei, meaning "tears (weeping)" in Chinese, derives from the Chinese name for this star.[11]
Ancha belongs to thespectral class G8 with aluminosity class of III–IV suggesting that, at an age of 437[3] million years, this star is part way between thesubgiant andgiant stages of itsevolution. Estimates of the star's mass range from 2.39[5] to 2.78[3] timesthe Sun's mass, with a radius of about 12[4] times thatof the Sun. It is radiating from 72[4] to 83[3] times as much luminosityas the Sun from its enlargedouter envelope at aneffective temperature of 4,864 K.[4] At this heat, the star glows with the yellow hue of aG-type star.[12]
