Theta Serpentis

θ Serpentis
Location of θ Serpentis (circled in red)
Observation data
Epoch J2000.0      Equinox ICRS
Constellation Serpens
θ1 Ser
Right ascension 18h 56m 13.18720s
Declination +04° 12′ 12.9821″
Apparent magnitude (V) +4.62
θ2 Ser
Right ascension 18h 56m 14.64102s
Declination +04° 12′ 07.6594″
Apparent magnitude (V) +4.98
Characteristics
θ1 Ser
Spectral type A5V
θ2 Ser
Evolutionary stage main sequence
Spectral type A5Vn
Astrometry
θ1 Ser
Proper motion (μ) RA: +46.374 mas/yr
Dec.: +31.313 mas/yr
Parallax (π)24.2696±0.1753 mas
Distance134.4 ± 1.0 ly
(41.2 ± 0.3 pc)
θ2 Ser
Proper motion (μ) RA: +50.044 mas/yr
Dec.: +28.363 mas/yr
Parallax (π)24.5310±0.1083 mas
Distance133.0 ± 0.6 ly
(40.8 ± 0.2 pc)
Position (relative to A)
ComponentB
Epoch of observation2019
Angular distance22.40″
Position angle106°
Projected separation900 AU
Details
θ1 Ser
Mass1.94±0.30 M☉
Radius2.21±0.07 R☉
Luminosity24 L☉
Surface gravity (log g)4.04±0.07 cgs
Temperature8,019±136 K
Rotational velocity (v sin i)130 km/s
Age594 Myr
θ2 Ser
Mass1.768±0.040 M☉
Radius2.094±0.044 R☉
Luminosity13.32+0.15
−0.17 L☉
Surface gravity (log g)3.99 cgs
Temperature7,631+11
−10 K
Rotational velocity (v sin i)220 km/s
Age390 Myr
Other designations
63 Serpentis, ADS 11853, CCDM 18563+0413, WDS 18562+0412
θ1 Ser: Alya, θ Ser A, HR 7141, HD 175638, SAO 124068, HIP 92946, WDS 18562+0412A
θ2 Ser: θ Ser B, HR 7142, HD 175639, SAO 124070, HIP 92951, WDS 18562+0412B
Database references
SIMBADθ Ser
θ1 Ser
θ2 Ser

Theta Serpentis (θ Serpentis, abbreviated Theta Ser, θ Ser) is a binary star in the constellation of Serpens. It is visible to the naked eye with a combined apparent magnitude of 4.0. Based on parallax measurements, it lies about 130 light-years distant.

The two components are designated Theta Serpentis A (officially named Alya /ˈæliə/, the traditional name for the entire system), also called Theta1 Serpentis, and B, also called Theta2 Serpentis.

Nomenclature

θ Serpentis (Latinised to Theta Serpentis) is the system's Bayer designation; θ1 and θ2 Serpentis those of the brightest two components. The designations of the two constituents as Theta Serpentis AB and C, and those of AB's components - Theta Serpentis A and B - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).

The system bore the traditional name Alya, or Alga, from the Arabic الية ’alyah "fat tail (of a sheep)". In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name Alya for the component Theta Serpentis A on 21 August 2016 and it is now so included in the List of IAU-approved Star Names.

In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Dzaneb al Haiyet, which was translated into Latin as Cauda Serpentis, meaning 'the serpent's tail'.

In Chinese, 天市左垣 (Tiān Shì Zuǒ Yuán), meaning Left Wall of Heavenly Market Enclosure, refers to an asterism which represents eleven old states in China, consisting of Theta Serpentis, Delta Herculis, Lambda Herculis, Mu Herculis, Omicron Herculis, 112 Herculis, Zeta Aquilae, Eta Serpentis, Nu Ophiuchi, Xi Serpentis and Eta Ophiuchi. Consequently, the Chinese name for Theta Serpentis itself is 天市左垣七 (Tiān Shì Zuǒ Yuán qī, English: the Seventh Star of Left Wall of Heavenly Market Enclosure), representing the state Xu (徐).

Properties

Both Theta1 Serpentis and Theta2 Serpentis are A-type main sequence stars. As of 2019, these two stars are 22 arcseconds apart on the sky along a position angle of 106°, values that changed little since the first observations in 1755. At the system's distance, the angular separation give a projected separation of 900 astronomical units, implying an orbital period in the order of 10,000 years. θ1 has an apparent magnitude of +4.62 while the slightly dimmer θ2 has a magnitude of +4.98. Both stars are similar to each other in all respects, having luminosities of 24 and 13 times solar, masses of 2.0 and 1.8 solar masses, radii of about twice solar and effective temperatures of 8,000 and 7,600 K, respectively.

The magnitude 6.71 star HD 175726 (Theta Serpentis C) is an optical companion to the pair. As of 2007, it is separated by 421" from A and 405" from B. It is not gravitationally bound to the pair since its distance to Earth is 87 light-years, much closer than the AB pair. Its proper motion is also discrepant with that of Theta Serpentis. It is a G-type main-sequence star with about the same mass and radius as the Sun.

References

  1. 1 2 3 4 5 6 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.
  2. 1 2 3 Hoffleit, Dorrit; Jaschek, Carlos (1991). "The Bright star catalogue". New Haven. Bibcode:1991bsc..book.....H.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 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.
  4. 1 2 3 Abt, Helmut A.; Morrell, Nidia I. (1995). "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars". Astrophysical Journal Supplement. 99: 135. Bibcode:1995ApJS...99..135A. doi:10.1086/192182.
  5. 1 2 3 4 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. Bibcode:2001AJ....122.3466M. doi:10.1086/323920.
  6. 1 2 Kaler, Jim. "Alya". www.astro.uiuc.edu. Archived from the original on 2008-12-07. Retrieved 2025-03-11.
  7. 1 2 3 4 5 Stassun, Keivan G.; Oelkers, Ryan J.; Paegert, Martin; Torres, Guillermo; Pepper, Joshua; De Lee, Nathan; Collins, Kevin; Latham, David W.; Muirhead, Philip S.; Chittidi, Jay; Rojas-Ayala, Bárbara; Fleming, Scott W.; Rose, Mark E.; Tenenbaum, Peter; Ting, Eric B. (2019-10-01). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467. ISSN 0004-6256. Theta2 Serpentis' database entry at VizieR.
  8. 1 2 McDonald, I.; Zijlstra, A. A.; Boyer, M. L. (2012). "Fundamental parameters and infrared excesses of Hipparcos stars". Monthly Notices of the Royal Astronomical Society. 427 (1): 343–357. arXiv:1208.2037. Bibcode:2012MNRAS.427..343M. doi:10.1111/j.1365-2966.2012.21873.x. S2CID 118665352.
  9. 1 2 Howe, K. S.; Clarke, C. J. (2009). "An analysis of v sin (I) correlations in early-type binaries". Monthly Notices of the Royal Astronomical Society. 392 (1): 448. Bibcode:2009MNRAS.392..448H. doi:10.1111/j.1365-2966.2008.14073.x.
  10. 1 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. arXiv:1501.03154. Bibcode:2015ApJ...804..146D. doi:10.1088/0004-637X/804/2/146.
  11. ↑ "Theta Serpentis". www.havastro.co.uk. Retrieved 2025-03-11.
  12. ↑ Davis, George A. (1944). "The pronunciations, derivations, and meanings of a selected list of star names". Popular Astronomy. 52: 8–30. Bibcode:1944PA.....52....8D.
  13. 1 2 "Naming Stars". IAU.org. Retrieved 6 March 2018.
  14. ↑ Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].
  15. ↑ 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.
  16. ↑ "IAU Working Group on Star Names (WGSN)". International Astronomical Union. Retrieved 22 May 2016.
  17. ↑ "WG Triennial Report (2015-2018) - Star Names" (PDF). p. 5. Retrieved 2018-07-14.
  18. ↑ Knobel, E. B. (June 1895). "Al Achsasi Al Mouakket, on a catalogue of stars in the Calendarium of Mohammad Al Achsasi Al Mouakket". Monthly Notices of the Royal Astronomical Society. 55 (8): 429. Bibcode:1895MNRAS..55..429K. doi:10.1093/mnras/55.8.429.
  19. ↑ (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.
  20. ↑ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2008-10-25 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
  21. ↑ (in Chinese) English-Chinese Glossary of Chinese Star Regions, Asterisms and Star Name Archived 2010-08-10 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
  22. ↑ Høg, E.; et al. (2000), "The Tycho-2 catalogue of the 2.5 million brightest stars", Astronomy and Astrophysics, vol. 355, pp. L27, Bibcode:2000A&A...355L..27H, doi:10.1888/0333750888/2862, ISBN 0333750888
  23. ↑ "HD 175726". SIMBAD. Centre de données astronomiques de Strasbourg.
  24. ↑ 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.
  25. ↑ Houk, N.; Swift, C. (1999). "Michigan catalogue of two-dimensional spectral types for the HD Stars". Michigan Spectral Survey. 5. Bibcode:1999MSS...C05....0H.
  26. ↑ Boyajian, Tabetha S.; et al. (July 2013). "Stellar Diameters and Temperatures. III. Main-sequence A, F, G, and K Stars: Additional High-precision Measurements and Empirical Relations". The Astrophysical Journal. 771 (1): 31. arXiv:1306.2974. Bibcode:2013ApJ...771...40B. doi:10.1088/0004-637X/771/1/40. S2CID 14911430. 40. See Table 3.