Theta Aquilae
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Star θ Aquilae |
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| Aquila constellation | |||||||||||||||||
| AladinLite | |||||||||||||||||
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Observation dates equinox : J2000.0 , epoch : J2000.0 |
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| Constellation | Eagle | ||||||||||||||||
| Right ascension | 20 h 11 m 18.29 s | ||||||||||||||||
| declination | -00 ° 49 ′ 17.3 ″ | ||||||||||||||||
| Apparent brightness | 3.24 mag | ||||||||||||||||
| Typing | |||||||||||||||||
| B − V color index | −0.07 | ||||||||||||||||
| U − B color index | −0.14 | ||||||||||||||||
| R − I index | −0.05 | ||||||||||||||||
| Spectral class | B9.5 III | ||||||||||||||||
| Astrometry | |||||||||||||||||
| Radial velocity | −27.3 km / s | ||||||||||||||||
| parallax | (11.39 ± 0.24) mas | ||||||||||||||||
| distance | (286.4 ± 6.0) Lj (87.8 ± 1.8) pc |
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| Visual absolute brightness M vis | −1.48 mag | ||||||||||||||||
| Proper movement | |||||||||||||||||
| Rec. Share: | (35.26 ± 0.35) mas / a | ||||||||||||||||
| Dec. portion: | (5.71 ± 0.18) mas / a | ||||||||||||||||
| Physical Properties | |||||||||||||||||
| Dimensions | 3.7 M ☉ | ||||||||||||||||
| radius | 5.5 R ☉ | ||||||||||||||||
| Luminosity |
370 L ☉ |
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| Effective temperature | 10800 K | ||||||||||||||||
| Rotation time | <4.9 days | ||||||||||||||||
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Other names and catalog entries |
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Theta Aquilae (θ Aql) is the fourth brightest star in the constellation Eagle . In Mandarin he has the classic proper name Tseen Foo (ie "heavenly raft", Chinese 天 桴 , pinyin tiānfú ). It has an apparent magnitude of 3.24 mag, is about 290 light years from Earth and has the spectral class B9.5. Therefore it appears bluish-white.
Theta Aquilae is wrongly classified as a giant , because its luminosity actually comes from two very close, inseparable stars: It is a spectroscopic binary star whose components have an orbital period of 17.123 days and an average distance of 0.24 AU . The orbit is relatively eccentric. Even if telescopes are not sufficient to resolve the double star, this can very well be done using interferometry . Both components are B9 stars, but the main star is more massive and brighter. He is a 3.47 likes bright sub giant with 3.7 times the mass, the 5.5 times the diameter and 370fachen luminosity of the sun, while the companion a 5.0 likes bright main sequence star with the 2.8 times mass, radius 2.7 times and 90 times the luminosity of the sun. The main component is a metal-rich star, so it has a relatively high proportion of heavier elements. At a distance of 113.7 ″ from Theta Aquilae there is a 13.0 mag bright star, but this is only likely to be an optical (i.e. not gravitationally bound) companion. Theta Aquilae is likely embedded in a large reflection nebula .