Phi Virginis Explained

Phi Virginis (φ Virginis, abbreviated Phi Vir, φ Vir) is a binary star in the zodiac constellation of Virgo. It can be seen with the naked eye, having an apparent visual magnitude of +4.81. Based upon parallax measurements obtained during the Hipparcos mission, it is located roughly 118abbr=offNaNabbr=off distant from the Sun.

The two components are designated Phi Virginis A (officially named Elgafar, the traditional name for the system)[1] and B.

Nomenclature

φ Virginis (Latinised to Phi Virginis) is the binary's Bayer designation. The designations of the two components as Phi Virginis 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).[2]

Ideler described an Arabic lunar mansion "El-ġafr" (Arabic الغفر al-ghafr) for the stars Phi, Iota and Kappa Virginis.[3] In 2016, the IAU organized a Working Group on Star Names (WGSN)[4] to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[5] It approved the name Elgafar for the component Phi Virginis A on 1 June 2018 and it is now so included in the List of IAU-approved Star Names.[1]

In Chinese, Chinese: 亢宿 (Chinese: Kàng Xiù), meaning Neck, refers to an asterism consisting of Phi Virginis, Kappa Virginis, Iota Virginis, and Lambda Virginis.[6] Consequently, Phi Virginis itself is known as Chinese: 亢宿三 (Chinese: Wěi Xiù sān), "the Third Star of Neck".[7]

Properties

The primary component, Phi Virginis A, has a stellar classification of G2 IV, indicating that it is a G-type subgiant which is evolving away from the main sequence. It is slightly variable with an amplitude of 0m.06. The star has about 1.8 times the mass of the Sun, 4 times the Sun's radius, and shines with 12.6 times the luminosity of the Sun. It is around 1.5 billion years old and is spinning with a projected rotational velocity of 15.5 km/s. The effective temperature of the star's outer atmosphere is 5,534 K.

The secondary, Phi Virginis B, is a magnitude 9.10 companion at an angular separation of 5.160 arcseconds. A second visual companion lies at an angular separation of 91.40 arcseconds along a position angle of 202°, as of 2000.

The system is a source of X-ray emission with a luminosity of .

Notes and References

  1. Web site: Naming Stars . IAU.org . 18 June 2018.
  2. On the naming convention used for multiple star systems and extrasolar planets . 2010 . 1012.0707 . astro-ph.SR . Hessman . F. V. . Dhillon . V. S. . Winget . D. E. . Schreiber . M. R. . Horne . K. . Marsh . T. R. . Guenther . E. . Schwope . A. . Heber . U. .
  3. Book: Ideler, Ludwig . Untersuchungen über den Ursprung und die Bedentung der Sternnamen . J. F. Weiss . 1809 .
  4. Web site: IAU Working Group on Star Names (WGSN). 22 May 2016.
  5. Web site: WG Triennial Report (2015-2018) - Star Names . 5 . 2018-07-14.
  6. 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, .
  7. 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.