Delta Aquarii
 Location of δ Aquarii (circled) |
|
| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Aquarius |
| Right ascension | 22h 54m 39.0125s[1] |
| Declination | −15° 49′ 14.953″[1] |
| Apparent magnitude (V) | 3.252[2] |
| Characteristics | |
| Spectral type | A3 V[3] |
| U−B color index | +0.172[2] |
| B−V color index | +0.068[2] |
| Astrometry | |
| Radial velocity (Rv) | +18.0[4] km/s |
| Proper motion (μ) | RA: -42.60[1] mas/yr Dec.: -27.89[1] mas/yr |
| Parallax (π) | 20.44 ± 2.26[1] mas |
| Distance | approx. 160 ly (approx. 49 pc) |
| Details | |
| Mass | 2.0[5] M☉ |
| Radius | 2.4[5] R☉ |
| Luminosity | 26[5] L☉ |
| Surface gravity (log g) | 3.66[6] cgs |
| Temperature | 9,000[6] K |
| Metallicity [Fe/H] | –0.15[6] dex |
| Rotational velocity (v sin i) | 81[7] km/s |
| Age | 0.3[8] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Delta Aquarii (δ Aqr, δ Aquarii) is the third-brightest star in the constellation Aquarius. It has the traditional name Skat,[10] which has also been used for Beta Pegasi. The apparent visual magnitude is 3.3,[2] which can be seen with the naked eye. The distance to this star is estimated as 160 light-years (49 parsecs) based upon parallax measurements.[1]
Properties
The spectrum of Skat matches a stellar classification of A3 V,[3] indicating this is an A-type main sequence star that is generating energy through the nuclear fusion of hydrogen at its core. This star has double the Sun's mass and a radius 2.4 times as large.[5] It is radiating 26[5] times the luminosity of the Sun from its outer atmosphere at an effective temperature of around 9,000 K.[6] This heat gives it the characteristic white-hued glow of an A-type star.[11] It has a relatively high rate of rotation, with a projected rotational velocity of 81 km s−1.[7]
Delta Aquarii has been closely examined for a companion, but none has been discovered.[8] Nor does it display a strong signal of excess infrared emission that might indicate the presence of circumstellar matter.[12] Delta Aquarii is a probable stream star member of the Ursa Major Moving Group,[13] which has an estimated age of 500 million years.[14]
In culture
The traditional name has generally been thought to derive from the Arabic as-saq (الساق) "leg" or "shin"; however, the medieval forms Scheat, Seat, Sheat suggest it may be instead from the Arabic ši'at (شئت) "wish".[1]
In Chinese, 羽林軍 (Yǔ Lín Jūn), meaning Palace Guard, refers to an asterism consisting of δ Aquarii, 29 Aquarii, 35 Aquarii, 41 Aquarii, 47 Aquarii, 49 Aquarii, λ Piscis Austrini, HD 212448, ε Piscis Austrini, 21 Piscis Austrini, 20 Piscis Austrini, υ Aquarii, 68 Aquarii, 66 Aquarii, 61 Aquarii, 53 Aquarii, 50 Aquarii, 56 Aquarii, 45 Aquarii, 58 Aquarii, 64 Aquarii, 65 Aquarii, 70 Aquarii, 74 Aquarii, τ2 Aquarii, τ1 Aquarii, 77 Aquarii, 88 Aquarii, 89 Aquarii, 86 Aquarii, 101 Aquarii, 100 Aquarii, 99 Aquarii, 98 Aquarii, 97 Aquarii, 94 Aquarii, ψ3Aquarii, ψ2Aquarii, ψ1Aquarii, 87 Aquarii, 85 Aquarii, 83 Aquarii, χ Aquarii, ω1 Aquarii and ω2 Aquarii. Consequently, δ Aquarii itself is known as 羽林軍二十六 (Yǔ Lín Jūn ershíliù, English: the Twenty Sixth Star of Palace Guard.)[15]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 2.0 2.1 2.2 2.3 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 3.0 3.1 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 5.0 5.1 5.2 5.3 5.4 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 6.0 6.1 6.2 6.3 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 7.0 7.1 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ 8.0 8.1 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
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- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 7 日
