Misplaced Pages

Iota Hydrae (ι Hydrae, abbreviated Iota Hya, ι Hya), formally named Ukdah /ˈʌkdə/, is a star in the constellation of Hydra, about 8° to the north-northwest of Alphard (Alpha Hydrae) and just to the south of the celestial equator. Visible to the naked eye, it is a suspected variable star with an apparent visual magnitude that ranges between 3.87 and 3.91. Based upon an annual parallax shift of 12.39 mas measured during the Hipparcos mission, it is located around 263 light-years from the Sun.

Nomenclature

ι Hydrae (Latinised to Iota Hydrae) is the star's Bayer designation.

This star along with Tau¹ Hydrae, Tau² Hydrae and 33 Hydrae (A Hydrae), were Ptolemy's Καμπή (Kampē); but Kazwini knew them as عقدة ʽuqdah (or ʽuḳdah) "knot". According to a 1971 NASA memorandum, Ukdah was the name of an asterism of four stars: Tau¹ Hydrae as Uḳdah I, Tau² Hydrae as Uḳdah II, 33 Hydrae as Uḳdah III and Iota Hydrae as Uḳdah IV. In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN approved the name Ukdah for Iota Hydrae on 1 June 2018 and it is now so included in the List of IAU-approved Star Names.

In Chinese, 星宿 (Xīng Sù), meaning Star or asterism, refers to an asterism consisting of ι Hydrae, Alphard, τ Hydrae, τ Hydrae, 26 Hydrae, 27 Hydrae, HD 82477 and HD 82428. Consequently, ι Hydrae are known as 星宿四 (Xīng Sù sì, English: the Fourth Star of Star).

Properties

This is an evolved K-type giant star with a stellar classification of K2.5 III. It is a Barium star, which means that, for a giant star, it displays unusually strong absorption lines of singly-ionized barium and strontium. Iota Hydrae has nearly twice the mass of the Sun and has expanded to 30 times the Sun's radius. It is around 2.5 billion years old and is spinning with a leisurely projected rotational velocity of 4.5 km/s. It may be a member of the Wolf 630 moving group of stars that share a common trajectory through space.

References

1. ^ van Leeuwen, F. (2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357, S2CID 18759600.
2. ^ Luck, R. Earle (September 2015), "Abundances in the Local Region. I. G and K Giants", The Astronomical Journal, 150 (3): 23, arXiv:1507.01466, Bibcode:2015AJ....150...88L, doi:10.1088/0004-6256/150/3/88, S2CID 118505114, 88.
3. ^ Samus, N. N.; Durlevich, O. V.; et al. (2009), "General Catalogue of Variable Stars", VizieR On-line Data Catalog, 1, Bibcode:2009yCat....102025S.
4. ^ Massarotti, Alessandro; et al. (January 2008), "Rotational and radial velocities for a sample of 761 HIPPARCOS giants and the role of binarity", The Astronomical Journal, 135 (1): 209–231, Bibcode:2008AJ....135..209M, doi:10.1088/0004-6256/135/1/209.
5. 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, S2CID 119257644.
6. ^ Baines, Ellyn K.; Armstrong, J. Thomas; Schmitt, Henrique R.; Zavala, R. T.; Benson, James A.; Hutter, Donald J.; Tycner, Christopher; Van Belle, Gerard T. (2018), "Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer", The Astronomical Journal, 155 (1): 30, arXiv:1712.08109, Bibcode:2018AJ....155...30B, doi:10.3847/1538-3881/aa9d8b, S2CID 119427037.
7. "iot Hya". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2017-01-04.{{cite web}}: CS1 maint: postscript (link)
8. ^ "Naming Stars". IAU.org. Retrieved 18 June 2018.
9. O'Meara, Steve (2007), Herschel 400 Observing Guide, Cambridge University Press, p. 84, ISBN 978-0521858939.
10. Moore, Patrick (2013), The Observer's Year: 366 Nights of the Universe, The Patrick Moore Practical Astronomy Series, Springer Science & Business Media, p. 71, ISBN 978-1447136132.
11. Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York, NY: Dover Publications Inc. p. 250. ISBN 0-486-21079-0. Retrieved 2010-12-12.
12. Jack W. Rhoads - Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars, Jet Propulsion Laboratory, California Institute of Technology; November 15, 1971
13. "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
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.
15. (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 29 日 Archived 2011-05-22 at the Wayback Machine
16. Lu, Phillip K. (June 1991), "Taxonomy of barium stars", Astronomical Journal, 101: 2229–2254, Bibcode:1991AJ....101.2229L, doi:10.1086/115845.
17. McDonald, A. R. E.; Hearnshaw, J. B. (August 1983), "The Wolf 630 moving group of stars", Monthly Notices of the Royal Astronomical Society, 204 (3): 841–852, Bibcode:1983MNRAS.204..841M, doi:10.1093/mnras/204.3.841.

• K-type giants
• Suspected variables
• Barium stars
• Hydra (constellation)
• Bayer objects
• Durchmusterung objects
• Flamsteed objects
• Henry Draper Catalogue objects
• Hipparcos objects
• Bright Star Catalogue objects
• Stars with proper names