Epoch J2000 Equinox J2000
|Right ascension||19h 36m 43.27606s|
|Declination||–01° 17′ 11.7611″|
|Apparent magnitude (V)||4.364|
|Spectral type||B5 III|
|U−B color index||–0.428|
|B−V color index||–0.083|
|R−I color index||–0.08|
|Radial velocity (Rv)||–21.4 km/s|
|Proper motion (μ)||RA: –0.87 mas/yr
Dec.: –20.39 mas/yr
|Parallax (π)||8.34 ± 0.79 mas|
|Distance||390 ± 40 ly
(120 ± 10 pc)
|Mass||4.8 ± 0.3 M☉|
|Radius||5.5 ± 0.5 R☉|
|Surface gravity (log g)||3.64 ± 0.05 cgs|
|Rotational velocity (v sin i)||55 km/s|
|Age||100 ± 8 Myr|
Iota Aquilae (ι Aql, ι Aquilae) is the Bayer designation for a star in the equatorial constellation of Aquila. It has the traditional name Al Thalimain, which it shares with λ Aquilae. The name is derived from the Arabic term الظليمان ath-thalīmain meaning "The Two Ostriches". With an apparent visual magnitude of 4.364, this star is bright enough to be seen with the naked eye. Based upon an annual parallax shift of 8.34 ± 0.79 mas, it is located at a distance of around 390 light-years (120 parsecs) from Earth. At that distance, the visual magnitude of the star is diminished by 0.15 from extinction caused by intervening gas and dust.
In Chinese, 右旗 (Yòu Qí), meaning Right Flag, refers to an asterism consisting of ι Aquilae, μ Aquilae, σ Aquilae, δ Aquilae, ν Aquilae, 42 Aquilae, HD 184701, κ Aquilae and 56 Aquilae. Consequently, ι Aquilae itself is known as 右旗五 (Yòu Qí wu, English: the Fifth Star of Right Flag.)
Although Iota Aquilae is listed in star catalogues as a giant star, calculations of its dimension show that in reality it is a main-sequence star. It has nearly five times the mass of the Sun and five to six times the Sun's radius. It is emitting 851 times the luminosity of the Sun from its outer atmosphere at an effective temperature of 14,552 K, giving it the blue-white hue of a B-type star. The projected rotational velocity of this star is 55 km/s. Even though it is only around 100 million years old, it has already spent 91% of its allotted lifetime on the main sequence.
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