Theta Aquarii
 Location of θ Aquarii (circled) |
|
| 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−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[1] mas |
| 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 | |
Theta Aquarii (θ Aqr, θ Aquarii) is the bayer designation for a star in the equatorial constellation of Aquarius. It has the traditional name Ancha; Medieval Latin for "the haunch". Visible to the naked eye at apparent magnitude 4.175,[2] it is located at a distance of around 187 light-years (57 parsecs) from Earth.[1] Since it is near the ecliptic it can be occulted by the Moon, or very rarely by planets.
In Chinese, 泣 (Qì), meaning Weeping, refers to an asterism consisting of θ Aquarii and ρ Aquarii.[7] Consequently, θ Aquarii itself is known as 泣二 (Qì èr, English: the Second Star of Weeping.).[8] Possibly, the name Lei meaning tears (weeping) in Chinese, was appear from the Chinese name for this star[9]
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.[10]
References
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- ↑ (Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
- ↑ (Chinese) 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.
- ↑ Richard Hinckley Allen: Star Names — Their Lore and Meaning: Aquarius
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
