Astronomy:Beta Capricorni

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Short description: Star system in the constellation Capricornus
β Capricorni
Beta Capricorni circled on a chart of Capricorn; the map is to be held up as with most sky maps so that the right of page is west.
Observation data
{{#ifeq:J2000.0|J2000.0 (ICRS)|Epoch J2000.0      Equinox J2000.0 (ICRS)| [[History:Epoch|Epoch J2000.0]]      [[Astronomy:Equinox (celestial coordinates)|Equinox J2000.0}}
Constellation Capricornus[1]
β1 Cap
Right ascension  20h 21m 00.6666s[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
β1 Cap
Spectral type K0II+B8V[5]
U−B color index +0.27[6]
B−V color index +0.79[6]
β2 Cap
Evolutionary stage main sequence[7][3]
Spectral type A0III[5]
U−B color index −0.11[8]
B−V color index −0.02[8]
Astrometry
β1 Cap
Radial velocity (Rv)−19.0±0.6[9] km/s
Proper motion (μ) RA: +44.133[2] mas/yr
Dec.: +0.360[2] mas/yr
Parallax (π)8.3966 ± 0.6348[2] mas
Distance390 ± 30 ly
(119 ± 9 pc)
Absolute magnitude (MV)−2.03[1]
β2 Cap
Proper motion (μ) RA: +44.411 mas/yr
Dec.: −0.637 mas/yr
Parallax (π)9.8983 ± 0.3071[3] mas
Distance330 ± 10 ly
(101 ± 3 pc)
Absolute magnitude (MV)+1.03[4]
Orbit[5]
PrimaryAa
CompanionAb
Period (P)3.762 yr
Semi-major axis (a)0.049″
Eccentricity (e)0.452
Inclination (i)75.1°
Semi-amplitude (K1)
(primary)		22.4 km/s
Semi-amplitude (K2)
(secondary)		19.6 km/s
Orbit[5]
PrimaryAb1
CompanionAb2
Period (P)8.677 days
Eccentricity (e)0.340
Semi-amplitude (K1)
(primary)		35.1 km/s
Orbit[5]
PrimaryBa
CompanionBb
Period (P)400 yr
Semi-major axis (a)0.689″
Eccentricity (e)0.458
Inclination (i)125.2°
Details
β1 Cap Aa
Mass3.69±0.20[10] M☉
Radius31.4[10] R☉
Luminosity501[10] L☉
Temperature4,870[10] K
Age230[10] Myr
β Cap Ab1
Mass4.22[5] M☉
Luminosity112[10] L☉
Age230[10] Myr
β Cap Ab2
Mass0.94[5] M☉
Age230[10] Myr
β Cap Ba
Mass2.53[5] M☉
Radius1.98[3] R☉
Luminosity55[3] L☉
Surface gravity (log g)4.18[3] cgs
Temperature11,188[3] K
Age230[10] Myr
β Cap Bb
Mass1.23[5] M☉
Age230[10] Myr
Other designations
Dabih, β Cap, 9 Capricorni, FK5 762, WDS J20210-1447AB
β1 Cap: Dabih Major, BD−15°5629, HD 193495, HIP 100345, HR 7776, WDS J20210-1447A
β2 Cap: Dabih Minor, BD−15°5626, HD 193452, HIP 100325, HR 7775, WDS J20210-1447B
Database references
SIMBADβ1 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.[9] Because it is positioned near the ecliptic, Beta Capricorni can be occulted by the Moon,[11] and also (rarely) by planets.

The system is believed to consist of five stars.[5] 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)[12][13] 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,[14] it is unclear whether they are simply optical doubles or part of the Beta Capricorni system.[15]

Nomenclature

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).[16]

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.[17] In 2016, the IAU organized a Working Group on Star Names (WGSN)[18] to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[19] 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.[13]

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.[20] Consequently, the Chinese name for Beta Capricorni itself is 牛宿一 (Niú Su yī, English: the First Star of Ox).[21]

Properties

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. If gravitationally bound, they would take around a million years to complete one orbit.[5]

Aa
Sep. = 0.05″
Ab1
Period = 8.7d
Ab2
Ba
Sep. = 3″
Bb

Hierarchy of orbits in the β Capricorni system

Beta1 Capricorni

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, and the close binary system Beta Capricorni Ab. They are separated by 0.04 arcseconds (5 AU[22]) and have an orbital period of 3.77 years.[5] Beta1 Capricorni is sufficiently close to the ecliptic to be occulted by the Moon.[22]

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.[22] The Ab1 and Ab2 components are separated by about 0.1 au[22] 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 have a published spectral class, but is estimated to have 0.94 times the mass of the Sun.[5]

Beta2 Capricorni

Beta2 Capricorni is a simpler single-lined spectroscopic binary. The visible component, Beta Capricorni Ba, is an A-type star with 40 times the luminosity of the Sun. The companion, Beta Capricorni Bb, is approximately 3 arcseconds from Ba and has a mass slightly higher than the Sun. Ba is classified as a mercury-manganese star, a chemically peculiar star with unusually strong mercury and manganese lines in its spectrum.[23]

Despite the luminosity class of III, the visible component of Beta2 Capricorni is apparently a main sequence star.[3][7]

References

  1. ↑ 1.0 1.1 1.2 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A  XHIP record for this object at VizieR.
  2. ↑ 2.0 2.1 2.2 2.3 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  4. ↑ 4.0 4.1 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A  XHIP record for this object at VizieR.
  5. ↑ 5.00 5.01 5.02 5.03 5.04 5.05 5.06 5.07 5.08 5.09 5.10 5.11 5.12 Tokovinin, Andrei (2018-03-01). "The Updated Multiple Star Catalog". The Astrophysical Journal Supplement Series 235 (1): 6. doi:10.3847/1538-4365/aaa1a5. ISSN 0067-0049. Bibcode: 2018ApJS..235....6T. 
  6. ↑ 6.0 6.1 Mallama, A. (2014). "Sloan Magnitudes for the Brightest Stars". Journal of the American Association of Variable Star Observers (Jaavso) 42 (2): 443. Bibcode: 2014JAVSO..42..443M. 
  7. ↑ 7.0 7.1 Takeda, Yoichi; Takada-Hidai, Masahide; Jugaku, Jun; Sakaue, Akihiko; Sadakane, Kozo (1999). "Oxygen 6156-8 Angstroms Triplet in Chemically Peculiar Stars of the Upper Main Sequence: Do HGMN Stars Show an Oxygen Anomaly?". Publications of the Astronomical Society of Japan 51: 961. doi:10.1093/pasj/51.6.961. Bibcode: 1999PASJ...51..961T. 
  8. ↑ 8.0 8.1 Renson, P.; Manfroid, J. (2009). "Catalogue of Ap, HGMN and Am stars". Astronomy and Astrophysics 498 (3): 961. doi:10.1051/0004-6361/200810788. Bibcode: 2009A&A...498..961R. 
  9. ↑ 9.0 9.1 Gontcharov, G. A. (2006). "Pulkovo compilation of radial velocities for 35495 stars in a common system". Astronomy Letters 32 (11): 759–771. doi:10.1134/S1063773706110065. Bibcode: 2006AstL...32..759G. 
  10. ↑ 10.00 10.01 10.02 10.03 10.04 10.05 10.06 10.07 10.08 10.09 Evans, D. S.; Fekel, ((F. C., Jr.)) (1979). "Beta Capricorni: Fundamental parameters from occultation astrometry and spectroscopy". The Astrophysical Journal 228: 497. doi:10.1086/156872. Bibcode: 1979ApJ...228..497E. 
  11. ↑ White, Nathaniel M.; Feierman, Barry H. (September 1987). "A Catalog of Stellar Angular Diameters Measured by Lunar Occultation". Astronomical Journal 94: 751. doi:10.1086/114513. Bibcode: 1987AJ.....94..751W. 
  12. ↑ 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. 
  13. ↑ 13.0 13.1 "Naming Stars". IAU.org. https://www.iau.org/public/themes/naming_stars/. 
  14. ↑ Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal 122 (6): 3466. doi:10.1086/323920. Bibcode: 2001AJ....122.3466M. 
  15. ↑ Hoffleit, D.; Warren, W. H. (1995). "VizieR Online Data Catalog: Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)". VizieR On-line Data Catalog: V/50. Originally Published in: 1964BS....C......0H 5050. Bibcode: 1995yCat.5050....0H. 
  16. ↑ Hessman, F. V.; et al. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].
  17. ↑ Allen, Richard Hinckley (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc.. p. 140. ISBN 0-486-21079-0. https://archive.org/details/starnamestheirlo00alle/page/140. 
  18. ↑ "IAU Working Group on Star Names (WGSN)". International Astronomical Union. https://www.iau.org/science/scientific_bodies/working_groups/280/. 
  19. ↑ "WG Triennial Report (2015-2018) - Star Names". p. 5. https://www.iau.org/static/science/scientific_bodies/working_groups/280/wg-starnames-triennial-report-2015-2018.pdf. 
  20. ↑ Script error: The function "in_lang" does not exist. 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.
  21. ↑ Script error: The function "in_lang" does not exist. 香港太空館 - 研究資源 - 亮星中英對照表 , Hong Kong Space Museum. Accessed on line November 23, 2010.
  22. ↑ 22.0 22.1 22.2 22.3 Kaler, James B.. "Dabih". http://stars.astro.illinois.edu/sow/dabih.html. 
  23. ↑ Ghazaryan, S.; Alecian, G.; Hakobyan, A. A. (2018). "New catalogue of chemically peculiar stars, and statistical analysis". Monthly Notices of the Royal Astronomical Society 480 (3): 2953. doi:10.1093/mnras/sty1912. Bibcode: 2018MNRAS.480.2953G. 



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