Xi Sagittarii
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| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Sagittarius |
| Right ascension | 18h 57m 20.5s |
| Declination | −20° 39' 23" |
| Apparent magnitude (V) | +5.02 |
| Distance | > 2300 ly (> 700 pc) |
| Spectral type | B9.5Ib |
| Other designations | |
The Bayer designation Xi Sagittarii (Xi Sgr, ξ Sagittarii, ξ Sgr) is shared by two stars, ξ¹ Sagittarii and ξ² Sagittarii, in the constellation Sagittarius, separated by 0.46° in the sky. Because they are close to the ecliptic, they can be occulted by the Moon[1] and, very rarely, by planets. The last occultation of ξ² Sagittarii by a planet took place on 22 December 1810, when it was occulted by Venus.
ξ¹ Sagittarii
Xi¹ Sagittarii (Xi¹ Sgr, ξ¹ Sagittarii, ξ¹ Sgr) is a spectral type B9.5 supergiant which has an apparent magnitude of +5.08. It is at least 2300 light years from Earth.
ξ² Sagittarii
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| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Sagittarius |
| Right ascension | 18h 57m 43.8s |
| Declination | −21° 06' 24" |
| Apparent magnitude (V) | +3.52 |
| Distance | 372 ± 42 ly (114 ± 13 pc) |
| Spectral type | G8/K0II/III |
| Other designations | |
Xi² Sagittarii (Xi² Sgr, ξ² Sagittarii, ξ² Sgr) is a spectral type G8 or K0 giant which has an apparent magnitude of +3.52. It is 372 light years from Earth.
Naming
In Chinese, 建 (Jiàn), meaning Establishment, refers to an asterism consisting of ξ² Sagittarii, ο Sagittarii, π Sagittarii, 43 Sagittarii, ρ¹ Sagittarii and υ Sagittarii. Consequently, ξ² Sagittarii itself is known as 建一 (Jiàn yī, English: the First Star of Establishment.)[2]
References
- ^ White, Nathaniel M.; Feierman, Barry H. (September 1987), "A Catalog of Stellar Angular Diameters Measured by Lunar Occultation", Astronomical Journal, 94: 751, Bibcode:1987AJ.....94..751W, doi:10.1086/114513.
- ^ Template:Zh icon AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 11 日
- "HD 175687 -- High proper-motion Star". SIMBAD Astronomical Database. Retrieved 2007-03-29.
- "HD 175775 -- High proper-motion Star". SIMBAD Astronomical Database. Retrieved 2007-03-29.
