Alphard

From Wikipedia, the free encyclopedia
(Redirected from Cor Hydrae)
Jump to navigation Jump to search

Template:Short description Template:Hatnote group

Alphard
Template:Location mark
Location of Alphard (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Hydra
Right ascension Template:RA[1]
Declination Template:DEC[1]
Apparent magnitude (V) +2.00[2]
Characteristics
Evolutionary stage Giant star
Spectral type K3IIIa[3]
U−B Template:Engvar +1.73[4]
B−V Template:Engvar +1.45[3]
Astrometry
Radial velocity (Rv)−4.3[5] km/s
Proper motion (μ) RA: −14.49[1] mas/yr
Dec.: 33.25[1] mas/yr
Parallax (π)18.40±0.78 mas[1]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)Template:Val[3]
Details
MassTemplate:Val[3] Template:Solar mass
RadiusTemplate:Val[6] Template:Solar radius
LuminosityTemplate:Val[3] Template:Solar luminosity
Luminosity (visual, LV)426[3]Template:Efn Template:Solar luminosity
Surface gravity (log g)1.77[7] cgs
TemperatureTemplate:Val[3] K
Metallicity [Fe/H]−0.12[7] dex
Rotation2,991 days[8]
Rotational velocity (v sin i)1.1[8] km/s
AgeTemplate:Val[9] Myr
Metallicity [Fe/H]{{{metal_fe2}}} dex
Other designations
Alphard, Alfard, Alphart, Kalbelaphard, Cor Hydrae, 30 Hydrae, HR 3748, BD−08°2680, HD 81797, SAO 136871, FK5 354, HIP 46390[10]
Database references
SIMBADdata

Script error: No such module "Check for unknown parameters".

Alphard (Template:IPAc-en[11]) is the brightest star in the constellation of Hydra. It has the Bayer designation Alpha Hydrae, which is that is Latinized from α Hydrae, and abbreviated Alpha Hya or α Hya. It is a giant star, cooler than the Sun but larger and more luminous. It is about 177 light-years away.

Nomenclature

α Hydrae (Latinised to Alpha Hydrae) is the star's Bayer designation.

The traditional name Alphard is from the Arabic الفرد (al-fard), "the individual", there being no other bright stars near it. It was also known as the "backbone of the Serpent" to the Arabs. In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, it was designated Soheil al Fard, which was translated into Latin as Soheil Solitarius, meaning the bright solitary one.[12] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[13] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[14] included a table of the first two batches of names approved by the WGSN; which included Alphard for this star. It is now so entered in the IAU Catalog of Star Names.[15]

The Danish astronomer Tycho Brahe dubbed it Cor Hydræ, Latin for 'the heart of Hydra'.[16]

In Chinese, Script error: No such module "Lang". (Script error: No such module "Lang".), meaning Star, refers to an asterism consisting of Alphard, τ1 Hydrae, τ2 Hydrae, ι Hydrae, 26 Hydrae, 27 Hydrae, HD 82477 and HD 82428.[17] Consequently, Alphard itself is known as Script error: No such module "Lang". (Script error: No such module "Lang".), "the First Star of Star".[18] In ancient China it formed part of an asterism called the "red bird".

Properties

File:HydraCC.jpg
The western portion of Hydra, with Alphard the brightest star near the centre

Alphard has three times the mass of the Sun.[3] Its estimated age is 420 million years[9] and it has evolved away from the main sequence to become a giant star with a spectral classification of K3 and luminosity class III.[3] The angular diameter has been measured using interferometry, after correction for limb darkening, it yields a value of Template:Val. Assuming the distance of Template:Convert, it yields a physical size of 57.6 times the radius of the Sun.[6]

Alphard's spectrum shows a mild excess of barium, an element that is normally produced by the s-process of nucleosynthesis. Typically a barium star belongs to a binary system and the anomalies in abundances are explained by mass transfer from a companion white dwarf star.[19]

Precise radial velocity measurements have shown variations in the stellar radial velocities and spectral line profiles. The oscillations are multi-periodic with periods from several hours up to several days. The short-term oscillations were assumed to be a result of stellar pulsations, similar to the solar ones. A correlation between the variations in the asymmetry of the spectral line profile and the radial velocity has also been found. The multi-periodic oscillations make HD 81797 (Alphard) an object of interest for asteroseismologic investigations.[20]

Modern legacy

Alphard appears on the flag of Brazil, symbolising the state of Mato Grosso do Sul.[21]

The Toyota Alphard is a minivan named after this star.

The character Roy Alphard from Japanese light novel series Re:Zero is named after this star.

Notes

Template:Notelist

References

Template:Reflist Template:Sky Template:Stars of Hydra

  1. ↑ a b c d e Cite error: Invalid <ref> tag; no text was provided for refs named hipparcos
  2. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named aaa526_A100
  3. ↑ a b c d e f g h i Cite error: Invalid <ref> tag; no text was provided for refs named rosas-portilla
  4. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named aj76
  5. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named rgcrv
  6. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named Baines2025
  7. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named piau
  8. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named aaa421_241
  9. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named aaa458
  10. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named SIMBAD
  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. ↑ Script error: No such module "citation/CS1".
  17. ↑ 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.
  18. ↑ Template:In lang 香港太空館 - 研究資源 - 亮星中英對照表 Template:Webarchive, Hong Kong Space Museum. Accessed on line November 23, 2010.
  19. ↑ Script error: No such module "Citation/CS1".
  20. ↑ Script error: No such module "Citation/CS1".
  21. ↑ Script error: No such module "citation/CS1".
Retrieved from "http://debianws.lexgopc.com/wiki143/index.php?title=Alphard&oldid=1154337"