Phact
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Double star α Columbae |
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Observation dates equinox : J2000.0 , epoch : J2000.0 |
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| Constellation | Dove | ||||||||||||||
| Right ascension | 05 h 39 m 38.94 s | ||||||||||||||
| declination | -34 ° 04 ′ 26.8 ″ | ||||||||||||||
| Apparent brightness | 2.65 likes | ||||||||||||||
| Typing | |||||||||||||||
| B − V color index | −0.12 | ||||||||||||||
| U − B color index | −0.46 | ||||||||||||||
| R − I index | −0.09 | ||||||||||||||
| Spectral class | B7 IV | ||||||||||||||
| Astrometry | |||||||||||||||
| Radial velocity | (35.0 ± 4.0) km / s | ||||||||||||||
| parallax | (12.48 ± 0.36) mas | ||||||||||||||
| distance | (261 ± 7) ly (80.1 ± 2.3) pc |
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| Visual absolute brightness M vis | −1.87 mag | ||||||||||||||
| Proper movement | |||||||||||||||
| Rec. Share: | (1.58 ± 0.28) mas / a | ||||||||||||||
| Dec. portion: | (−24.82 ± 0.50) mas / a | ||||||||||||||
| Physical Properties | |||||||||||||||
| Dimensions | 4.5 M ☉ | ||||||||||||||
| radius | 7 R ☉ | ||||||||||||||
| Luminosity |
1000 L ☉ |
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| Effective temperature | 12 500 K | ||||||||||||||
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Other names and catalog entries |
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Phakt (also Phact or Phaet , from Arabic الفاخثة, DMG al-Fāḫita 'dove') is the proper name of the star α Columbae (Alpha Columbae) in the constellation Dove . Phakt is a sub-giant of the spectral class B7e and with an apparent magnitude of 2.65 mag the brightest star of the pigeon. Its distance from Earth is approximately 260 light years . Phakt, like most B stars, rotates very quickly (90 times faster than the sun), so that the rotation speed at the equator is more than 180 km / s. This leads to a flattening of the poles and the formation of a low-density gas disk that surrounds Phakt up to about two star radii away. This disk, excited by its central star, emits an emission line spectrum. Such stars are called Be stars (where the “e” stands for emission). Similar stars are Achernar , Alkione, and Gamma Cassiopeiae .
As a double star, Phakt has a companion that is only 12.3 mag bright at a distance of 13.5 ".