Sigma Hydrae

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Template:Short description

Sigma Hydrae
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Hydra
Right ascension Template:RA[1]
Declination Template:DEC[1]
Apparent magnitude (V) 4.48[2]
Characteristics
Spectral type K2 III[3]
U−B Template:Engvar +1.23[2]
B−V Template:Engvar +1.21[2]
Astrometry
Radial velocity (Rv)Script error: No such module "val".[4] km/s
Proper motion (μ) RA: −19.48[1] mas/yr
Dec.: −15.92[1] mas/yr
Parallax (π)8.75±0.25 mas[1]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)−0.84[5]
Details[6]
Mass3.07 Template:Solar mass
Radius27.6[7] Template:Solar radius
Luminosity295 Template:Solar luminosity
Surface gravity (log g)Script error: No such module "val".[8] cgs
TemperatureScript error: No such module "val". K
Metallicity [Fe/H]Script error: No such module "val".[8] dex
Age430 Myr
Metallicity [Fe/H]{{{metal_fe2}}} dex
Other designations
σ Hya, 5 Hydrae, BD+03°2026, FK5 1224, HD 73471, HIP 42402, HR 3418, SAO 116988[9]
Database references
SIMBADdata

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Sigma Hydrae (σ Hydrae, abbreviated Sigma Hya, σ Hya), also named Minchir Template:IPAc-en,[10] is a solitary[11] star in the equatorial constellation of Hydra. It is visible to the naked eye with an apparent visual magnitude of 4.48.[2] The estimated distance to this star from the Sun, based upon an annual parallax shift of 8.75 mas,[1] is around 370 light-years. At that distance, the visual magnitude of the star is diminished by an interstellar extinction factor of 0.16,[4] due to intervening dust.

Nomenclature

σ Hydrae (Latinised to Sigma Hydrae) is the system's Bayer designation.

It bore the traditional name Minchir, appearing as Minchir es-schudscha in Bode's large star atlas, Uranographia. The name which derived from the Arabic appelationمنخر الشجاع minkhar ash-shujāʽ "the nostril brave one" (the hydra) for this star. The name is erroneouslyScript error: No such module "Unsubst". spelt as Al Minliar al Shuja in the Yale Bright Star Catalogue.[12] In 2016, the IAU organized a Working Group on Star Names (WGSN)[13] to catalog and standardize proper names for stars. The WGSN approved the name Minchir for this star on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.[10]

This star, along with Delta Hydrae (Lisan al Shudja), Epsilon Hydrae, Zeta Hydrae, Eta Hydrae and Rho Hydrae, were Ulug Beg's Min al Azʽal, "Belonging to the Uninhabited Spot".[14] (According to a 1971 NASA memorandum, Min al Azʽal or Minazal were the title for five stars : Delta Hydrae as Minazal I, Eta Hydrae as Minazal II, Epsilon Hydrae as Minazal III, Rho Hydrae as Minazal IV and Zeta Hydrae as Minazal V.[15])

In Chinese, Script error: No such module "Lang". (Script error: No such module "Lang".), meaning Willow (asterism), refers to an asterism consisting of Sigma Hydrae, Delta Hydrae, Eta Hydrae, Rho Hydrae, Epsilon Hydrae, Zeta Hydrae, Omega Hydrae and Theta Hydrae.[16] Consequently, Sigma Hydrae itself is known as Script error: No such module "Lang". (Script error: No such module "Lang"., Template:Langx).[17]

The people of Groote Eylandt, used the name Unwala ("The Crab") for the star cluster including this star, Delta Hydrae (Lisan al Shudja), Epsilon Hydrae, Zeta Hydrae, Eta Hydrae and Rho Hydrae.[18]

Properties

This is an evolved K-type giant star with a stellar classification of K2 III.[3] The measured angular diameter of this star, after correction for limb darkening, is Script error: No such module "val"..[19] At its estimated distance, this yields a physical size of about 27.6 times the radius of the Sun.[7] It has about three times the mass of the Sun and radiates 295 times the solar luminosity from its outer atmosphere at an effective temperature of 4,491 K. Sigma Hydrae is around 430 million years old.[6]

References

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  1. ↑ a b c d e f Script error: No such module "citation/CS1".
  2. ↑ a b c d Script error: No such module "citation/CS1".
  3. ↑ a b Script error: No such module "citation/CS1".
  4. ↑ a b Script error: No such module "citation/CS1".
  5. ↑ Script error: No such module "citation/CS1".
  6. ↑ a b Script error: No such module "citation/CS1".
  7. ↑ a b Script error: No such module "citation/CS1".. The radius (R*) is given by:
    2⋅R*=(114⋅2.25⋅10−3) AU0.0046491 AU/R⨀≈55.2⋅R⨀
  8. ↑ a b Script error: No such module "citation/CS1".
  9. ↑ Template:Cite simbad
  10. ↑ a b Script error: No such module "citation/CS1".
  11. ↑ Script error: No such module "citation/CS1".
  12. ↑ Script error: No such module "citation/CS1".
  13. ↑ Script error: No such module "citation/CS1".
  14. ↑ Script error: No such module "citation/CS1".
  15. ↑ Script error: No such module "citation/CS1".
  16. ↑ Template:In lang 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, Template:ISBN.
  17. ↑ Template:In lang AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 5 月 28 日 Template:Webarchive
  18. ↑ Script error: No such module "citation/CS1".
  19. ↑ Script error: No such module "citation/CS1".

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Template:Stars of Hydra

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