Astronomy:Theta Capricorni

From HandWiki
Short description: Binary star in the constellation Capricornus
Theta Capricorni
Location of θ Capricorni (circled)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Capricornus[1]
Right ascension  21h 05m 56.82783s[2]
Declination −17° 13′ 58.3021″[2]
Apparent magnitude (V) +4.07[3]
Characteristics
Evolutionary stage main sequence[4]
Spectral type A1 V[5]
U−B color index +0.01[3]
B−V color index −0.01[3]
Astrometry
Radial velocity (Rv)−10.9[6] km/s
Proper motion (μ) RA: +79.33[2] mas/yr
Dec.: −62.01[2] mas/yr
Parallax (π)20.11 ± 0.28[2] mas
Distance162 ± 2 ly
(49.7 ± 0.7 pc)
Absolute magnitude (MV)+0.60[1]
Orbit[7]
PrimaryA
CompanionB
Period (P)143 days
Semi-major axis (a)0.78 AU
Details[7]
A
Mass2.54 M☉
Radius2.35 R☉
Luminosity65[8] L☉
Surface gravity (log g)4.19±0.14[9] cgs
Temperature10,221 K
Metallicity [Fe/H]+0.26[1] dex
Rotational velocity (v sin i)104[9] km/s
Age280 Myr
B
Mass0.56 M☉
Radius0.52 R☉
Temperature3,900 K
Age280 Myr
Other designations
Udang, Dorsum, θ Cap, 23 Cap, BD−17°6174, FK5 1552, HD 200761, HIP 104139, HR 8075, SAO 164132[10]
Database references
SIMBADdata

Theta Capricorni, Latinized from θ Capricorni, (Theta Cap or θ Cap) formally named Udang,[11] is a binary star system in the southern constellation of Capricornus,[12] positioned 0.58° south of the ecliptic.[13] It can be seen with the naked eye, having an apparent visual magnitude of +4.07.[3] Based upon an annual parallax shift of 20.11 mas as seen from the Earth,[2] the star is about 162 light-years (50 pc) from the Sun. It is drifting closer with a radial velocity of −11 km/s.[6]

The star or star system is almost eclipsed by the Sun on about 3 February, when it will figure behind the Sun's corona if there is a full solar eclipse.[14] Thus the star can be viewed the whole night, crossing the sky, in early August (in the current epoch). It can be occulted by the Moon.[15]

Nomenclature

Theta Capricorni is the star's Bayer designation, which is Latinized from θ Capricorni and abbreviated Theta Cap or θ Cap. Sometimes (primarily in astrological sources), this star is called by the name Dorsum,[16] meaning the back (of the goat) in Latin.

Udang, the Shrimp, is a constellation from Bali (Indonesia), identified with Capricornus. It is anchored in the cultural calendar called Palelintangan which is attested for ~1300 years.[17] The IAU Working Group on Star Names approved the name Udang for Theta Capricorni A on 22 February 2026.[11]

In Chinese, 十二國 (Shíer Guó), meaning Twelve States, refers to an asterism which represents twelve ancient states in the Spring and Autumn period and the Warring States period, consisting of θ Capricorni, φ Capricorni, ι Capricorni, 38 Capricorni, 35 Capricorni, 36 Capricorni, χ Capricorni, 30 Capricorni, 33 Capricorni, ζ Capricorni, 19 Capricorni, 26 Capricorni, 27 Capricorni, 20 Capricorni, η Capricorni and 21 Capricorni.[18] Consequently, the Chinese name for θ Capricorni itself is 秦一 (Qin yī, English: the First Star of Qin), meaning that this star (together with 30 Capricorni[19]) and δ Serpentis in Right Wall of Heavenly Market Enclosure (asterism)[20] represents the state Qin (秦) (or Tsin).[20]

Characteristics

Radial velocity variations indicated it may be a binary star system,[21] but when the system was examined in the infrared, no companion was detected.[22] However, a companion was subsequently confirmed in 2023 by direct observations by an interferometer.[7]

The main component of this system is an A-type main sequence star with a stellar classification of A1 V.[5] Theta Capricorni has an estimated 2.54 times the mass of the Sun and around 2.35 times the Sun's radius. It is 280 million years old[7] and is spinning fairly rapidly with a projected rotational velocity of 104 km/s.[9] The star is radiating 65[8] times the solar luminosity from its photosphere at an effective temperature of around 10,000 K.[7]

The secondary component does not have a known stellar classification, but is much smaller and cooler than its primary, with about 50% the mass and radius of the Sun, and a temperature of 3,900 K. It takes 140 days (4.6 months) to complete an orbit around the barycenter, and is separated from its primary by 0.78 astronomical units.[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 2.4 2.5 van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, doi:10.1051/0004-6361:20078357, Bibcode: 2007A&A...474..653V. 
  3. ↑ 3.0 3.1 3.2 3.3 Johnson, H. L. et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory 4 (99): 99, Bibcode: 1966CoLPL...4...99J. 
  4. ↑ 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.
  5. ↑ 5.0 5.1 Cowley, A. et al. (April 1969), "A study of the bright A stars. I. A catalogue of spectral classifications", Astronomical Journal 74: 375–406, doi:10.1086/110819, Bibcode: 1969AJ.....74..375C. 
  6. ↑ 6.0 6.1 Wilson, R. E. (1953), "General Catalogue of Stellar Radial Velocities", Carnegie Institute Washington D.C. Publication (Carnegie Institution for Science), ISBN ((9780598216885)), Bibcode: 1953GCRV..C......0W. 
  7. ↑ 7.0 7.1 7.2 7.3 7.4 7.5 Waisberg, Idel et al. (June 2023), "Binarity and beyond in A stars – I. Survey description and first results of VLTI/GRAVITY observations of VAST targets with high Gaia–Hipparcos accelerations", Monthly Notices of the Royal Astronomical Society 521 (4): 5232–5254, doi:10.1093/mnras/stad872, ISSN 0035-8711, Bibcode: 2023MNRAS.521.5232W. 
  8. ↑ 8.0 8.1 McDonald, I. et al. (2012), "Fundamental Parameters and Infrared Excesses of Hipparcos Stars", Monthly Notices of the Royal Astronomical Society 427 (1): 343–57, doi:10.1111/j.1365-2966.2012.21873.x, Bibcode: 2012MNRAS.427..343M. 
  9. ↑ 9.0 9.1 9.2 David, Trevor J.; Hillenbrand, Lynne A. (2015), "The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets", The Astrophysical Journal 804 (2): 146, doi:10.1088/0004-637X/804/2/146, Bibcode: 2015ApJ...804..146D. 
  10. ↑ "tet Cap". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=tet+Cap. 
  11. ↑ 11.0 11.1 "IAU Catalog of Star Names". https://exopla.net/star-names/modern-iau-star-names/. 
  12. ↑ Kaler, James B. (September 12, 2008), "Theta Capricorni", Stars (University of Illinois), http://stars.astro.illinois.edu/sow/thetacap.html, retrieved 2017-05-09. 
  13. ↑ Pratt, John P. (February 10, 2016), "Zodiac Stars", John Pratt's Web Site, http://www.johnpratt.com/items/astronomy/zodiac/zodiac_stars.html, retrieved 2021-06-21. 
  14. ↑ In the Sky Earth astronomy reference utility showing the ecliptic and relevant date as at J2000 - present
  15. ↑ Eitter, J. J.; Beavers, W. I. (November 1974), "Lunar Occultation Summary. I", Astrophysical Journal Supplement 28: 405, doi:10.1086/190326, Bibcode: 1974ApJS...28..405E 
  16. ↑ "Dorsum", www.constellationsofwords.com, http://www.constellationsofwords.com/stars/Dorsum.html, retrieved 2017-05-16. 
  17. ↑ "Udang". IAU Working Group on Star Names. https://ase.exopla.net/index.php/Udang. 
  18. ↑ 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.
  19. ↑ Ridpath, Ian, "Capricornus the Sea Goat", Ian Ridpath's Startales, http://www.ianridpath.com/startales/capricornus.htm, retrieved 2025-08-04. 
  20. ↑ 20.0 20.1 Allen, Richard Hinckley (1963), "Capricornus", Star Names, Their Lore and Meaning, Dover, https://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Capricornus*.html, retrieved 2017-05-09. 
  21. ↑ Lagrange, A.-M. et al. (February 2009), "Extrasolar planets and brown dwarfs around A-F type stars. VI. High precision RV survey of early type dwarfs with HARPS", Astronomy and Astrophysics 495 (1): 335–352, doi:10.1051/0004-6361:200810105, Bibcode: 2009A&A...495..335L. 
  22. ↑ Ehrenreich, D. et al. (November 2010), "Deep infrared imaging of close companions to austral A- and F-type stars", Astronomy and Astrophysics 523: A73, doi:10.1051/0004-6361/201014763, Bibcode: 2010A&A...523A..73E. 



Retrieved from "https://handwiki.org/wiki/index.php?title=Astronomy:Theta_Capricorni&oldid=4287485"