| |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquarius |
| Right ascension | 22h16m 50.03635s[1] |
| Declination | –07° 46′ 59.8480″[1] |
| Apparent magnitude (V) | 4.175[2] |
| Characteristics | |
| Spectral type | G8 III–IV[3] |
| U−B color index | +0.818[2] |
| B−V color 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, abbreviated Theta Aqr, θ Aqr), officially named Ancha /ˈæŋkə/[7] (distinguish Ankaa, with the same pronunciation), is a star in the equatorial constellationofAquarius. Visible to the naked eye at apparent magnitude 4.175,[2] it is located at a distance of around 187 light-years (57parsecs) from the Sun.[1] Since it is near the ecliptic it can be occulted by the Moon, or very rarely by planets.
θ Aquarii (LatinisedtoTheta Aquarii) is the star's Bayer designation.
It bore the traditional name Ancha; Medieval Latin for "the haunch". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[8] to catalogue and standardize proper names for stars. The WGSN approved the name Ancha 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), meaning Weeping, refers to an asterism consisting of Theta Aquarii and Rho Aquarii.[9] Consequently, the Chinese name for Theta Aquarii itself is 泣二 (Qì èr, English: the Second Star of Weeping).[10] Possibly, the name Lei, meaning "tears (weeping)" in Chinese, derives from the Chinese name for this star.[11]
Ancha belongs to the spectral class G8 with a luminosity class of III–IV suggesting that, at an age of 437[3] million years, this star is part way between the subgiant and giant stages of its evolution. Estimates of the star's mass range from 2.39[5] to 2.78[3] times the Sun's mass, with a radius of about 12[4] times that of the Sun. It is radiating from 72[4] to 83[3] times as much luminosity as the Sun from its enlarged outer envelope at an effective temperature of 4,864 K.[4] At this heat, the star glows with the yellow hue of a G-type star.[12]
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