Beta Capricorni
  | |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Capricornus[1] |
| β1 Cap | |
| Right ascension | 20h 21m 0.6667s[2] |
| Declination | 14° 46′ 53.067″[2] |
| Apparent magnitude (V) | +3.05[1] |
| β2 Cap | |
| Right ascension | 20h 20m 46.5479s[3] |
| Declination | 14° 47′ 05.604″[3] |
| Apparent magnitude (V) | +6.09[4] |
| Characteristics | |
| Spectral type | K0II+B8V/A0III |
| U−B color index | 0.28/−0.11 |
| B−V color index | 0.79[1]/−0.016[4] |
| Astrometry | |
| Radial velocity (Rv) | −19.0±0.6[5] km/s |
| Proper motion (μ) | RA: +44.133 mas/yr[2] Dec.: +0.360 mas/yr[2] |
| Parallax (π) | 8.3966±0.6348 mas[2] |
| Distance | 390 ± 30 ly (119 ± 9 pc) |
| Absolute magnitude (MV) | −2.03[1]/+1.03[4] |
| Details | |
| β1 Cap Aa | |
| Mass | 4[6] M☉ |
| Radius | 35[6] R☉ |
| Luminosity | 600[6] L☉ |
| Temperature | 4,900[6] K |
| β Cap Ab1 | |
| Mass | 3.28[7] M☉ |
| β Cap Ab2 | |
| Mass | 0.94[7] M☉ |
| β Cap Ba | |
| Mass | 2.53[7] M☉ |
| β Cap Bb | |
| Mass | 1.23[7] M☉ |
| Other designations | |
| Dabih, Dabikh, Dikhabda, 9 Capricorni, FK5 762, WDS J20210-1447AB | |
| β1 Cap: BD−15°5629, HD 193495, HIP 100345, HR 7776, WDS J20210-1447A | |
| β2 Cap: BD−15°5626, HD 193452, HIP 100325, HR 7775, WDS J20210-1447B | |
| Database references | |
| SIMBAD | β Cap |
| β1 Cap | |
| β2 Cap | |
Beta Capricorni is a multiple star system in the constellation of Capricornus. Its name is a Bayer designation that is Latinized from β Capricorni, and abbreviated Beta Cap or β Cap. Based on Parallax measurements, it is located at a distance of approximately 390 light years from the Sun. The system is drifting closer with a line of sight velocity of −19 km/s.[5] Because it is positioned near the ecliptic, Beta Capricorni can be occulted by the Moon,[8] and also (rarely) by planets.
The system is believed to consist of five stars.[9] With binoculars or a small telescope, Beta Capricorni can be resolved into a binary pair. The brighter of the two is designated Beta1 Capricorni or Beta Capricorni A; the dimmer, Beta2 Capricorni or Beta Capricorni B. Both are themselves made up of multiple stars. Beta1 Capricorni has three components: a single star designated Beta Capricorni Aa (formally named Dabih /ˈdeɪbiː/, the traditional name of the system)[10][11] and a binary pair, Beta Capricorni Ab (whose two components are designated Beta Capricorni Ab1 and Ab2). Beta2 Capricorni is also a binary pair, with components designated Beta Capricorni Ba and Bb.
Two other nearby stars were discovered by John Herschel. Sometimes referred to as Beta Capricorni D and E, it is unclear whether they are simply optical doubles or part of the Beta Capricorni system.[citation needed]
Nomenclature
[edit]β Capricorni (Latinised to Beta Capricorni) is the system's Bayer designation; β1 and β2 Capricorni those of its two constituents. The designations of the two constituents as Beta Capricorni A and B, and those of the sub-components - Beta Capricorni Aa, Ab, Ab1, Ab2, Ba and Bb - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[12]
Beta Capricorni bore the traditional name Dabih, deriving from the Arabic الذابح al-dhābiḥ "the butcher", with Beta1 and Beta2 subsequently named Dabih Major and Dabih Minor, respectively.[13] In 2016, the IAU organized a Working Group on Star Names (WGSN)[14] to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[15] It approved the name Dabih for the component Beta Capricorni Aa on 21 August 2016 and it is now so included in the List of IAU-approved Star Names.[11]
In Chinese, 牛宿 (Niú Su), meaning Ox (asterism), refers to an asterism consisting of Beta Capricorni, Alpha2 Capricorni, Xi2 Capricorni, Pi Capricorni, Omicron Capricorni and Rho Capricorni.[16] Consequently, the Chinese name for Beta Capricorni itself is 牛宿一 (Niú Su yī, English: the First Star of Ox).[17]
Properties
[edit]Beta1 Capricorni is the brighter of the two components with an apparent magnitude of +3.05, while the dimmer Beta2 Capricorni has an apparent magnitude of +6.09. The two components are separated by 3.5 arcminutes on the sky, putting them at least 21,000 AU (0.34 light-years) apart. They take approximately 700,000 years to complete one orbit.
| Aa | |||||||||||||||||
| Sep. = 0.05″ | |||||||||||||||||
| Ab1 | |||||||||||||||||
| Period = 8.7d | |||||||||||||||||
| Ab2 | |||||||||||||||||
| Ba | |||||||||||||||||
| Sep. = 3″ | |||||||||||||||||
| Bb | |||||||||||||||||
Hierarchy of orbits in the β Capricorni system
Beta1 Capricorni
[edit]Beta1 Capricorni is the more complex of the pair and has a spectrum that is difficult to interpret. Its dominant pair of stars are the orange K-type bright giant Beta Capricorni Aa, with an apparent magnitude of +3.08, and the close binary system Beta Capricorni Ab1 with an apparent magnitude of +7.20.[citation needed] They are separated by 0.04 arcseconds (5 AU[6]) and have an orbital period of 3.77 years.[7] Beta1 Capricorni is sufficiently close to the ecliptic to be occulted by the Moon.[6]
The Aa component has a surface temperature of 4,900 K, a radius 35 times that of the Sun, and a luminosity 600 times that of the Sun.[6] The Ab1 and Ab2 components are separated by about 0.1 au[6] and complete an orbit around each other every 8.68 days. The Ab1 component is a B-type main-sequence star, while Ab2 does not has a spectral class, but is estimated to have 0.94 times the mass of the Sun.[7]
Beta2 Capricorni
[edit]Beta2 Capricorni is simpler and more studied. Its brighter component, Beta Capricorni Ba, has a magnitude of 6.1 and is an A0-giant with 40 times the luminosity of the Sun. The companion, Beta Capricorni Bb, is approximately 3 arcseconds from Ba. Ba is unusual for having large amounts of mercury and manganese in its atmosphere.
References
[edit]- ^ a b c d Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. XHIP record for this object at VizieR.
- ^ a b c d Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
- ^ a b Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
- ^ a b c Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. XHIP record for this object at VizieR.
- ^ a b Gontcharov, G. A. (2006). "Pulkovo compilation of radial velocities for 35495 stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
- ^ a b c d e f g h Kaler, James B. "Dabih". stars.astro.illinois.edu. Retrieved 2025-07-22.
- ^ a b c d e f Tokovinin, Andrei (2018-03-01). "The Updated Multiple Star Catalog". The Astrophysical Journal Supplement Series. 235 (1): 6. arXiv:1712.04750. Bibcode:2018ApJS..235....6T. doi:10.3847/1538-4365/aaa1a5. ISSN 0067-0049.
- ^ 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.
- ^ "Displaying next number in catalog HIP => 100345". Multiple Star Catalog. Archived from the original on 2018-07-26. Retrieved 2018-07-26.
- ^ Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.
- ^ a b "Naming Stars". IAU.org. Retrieved 18 June 2018.
- ^ Hessman, F. V.; et al. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].
- ^ Allen, Richard Hinckley (1963) [1899]. Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc. p. 140. ISBN 0-486-21079-0.
{{cite book}}: ISBN / Date incompatibility (help) - ^ "IAU Working Group on Star Names (WGSN)". International Astronomical Union. Retrieved 22 May 2016.
- ^ "WG Triennial Report (2015-2018) - Star Names" (PDF). p. 5. Retrieved 2018-07-14.
- ^ (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
- ^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2009-09-29 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
