Alpha Herculis

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Template:Short description

α Herculis
Template:Location mark
Location of α Herculis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Hercules
A
Right ascension Template:RA[1]
Declination Template:DEC[1]
Apparent magnitude (V) 3.350[1] (Template:Val[2])
B
Right ascension Template:RA[1]
Declination Template:DEC[1]
Apparent magnitude (V) 5.322[1]
Characteristics
A
Evolutionary stage AGB[3]
Spectral type M5 Ib-II[3]
U−B Template:Engvar +1.01[4]
B−V Template:Engvar +1.45[4]
Variable type SRc[2]
B
Spectral type G8III + A9IV-V[3]
Astrometry
Proper motion (μ) RA: −7.32[5] mas/yr
Dec.: 36.07[5] mas/yr
Parallax (π)9.07±1.32 mas[5]
Distanceapprox. Template:Rnd ly
(approx. Template:Rnd pc)
Absolute magnitude (MV)−2.3[6] + 1.8 + 2.8[7]
Details
A
MassTemplate:Val[8] Template:Solar mass
Radius284 ± 60, Template:Val[3] Template:Solar radius
LuminosityTemplate:Val[3] Template:Solar luminosity
Surface gravity (log g)Template:Val[9] cgs
TemperatureTemplate:Val[3] K
Metallicity [Fe/H]{{{metal_fe2}}} dex
Ba
Mass~2.5[3] Template:Solar mass
Luminosity126[3] Template:Solar luminosity
Temperature4,900[3] K
Bb
Mass~2[3] Template:Solar mass
Luminosity26[3] Template:Solar luminosity
Temperature7,350[3] K
Metallicity [Fe/H]{{{metal_fe2}}} dex
AgeTemplate:Val[3] Gyr
Other designations
Ras Algethi, Rasalgethi, α Her, 64 Her, BD+14°3207, HIP 84345, CCDM J17146+1424, AAVSO 1710+14, WDS J17146+1423[10]
A: HD 156014, HR 6406, SAO 102680
B: HD 156015, HR 6407, SAO 102681
Database references
SIMBADα Her
A
B

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Alpha Herculis (α Herculis, abbreviated Alpha Her, α Her), also designated Rasalgethi and 64 Herculis, is a multiple star system in the constellation of Hercules. Appearing as a single point of light to the naked eye, it is resolvable into a number of components through a telescope. It has a combined apparent magnitude of 3.08, although the brightest component is variable in brightness. Based on parallax measurements obtained during the Hipparcos mission, it is approximately 360 light-years (110 parsecs) distant from the Sun. It is also close to another bright star Rasalhague in the vicinity.

System

File:Double star Alpha Hercules.jpg
A view of Alpha Herculis in a small telescope. The components A and B are resolved with angular separation of 4.64'' (in 2020).

Alpha Herculis is a triple star system. The primary (brightest) of the three stars, designated α1 Herculis or α Herculis A, is a pulsating variable star on the asymptotic giant branch (AGB). The primary star forms a visual binary pair with a second star, which is itself a spectroscopic binary.[3]

Alpha Herculis also forms the A and B components of a wider system designated WDS J17146+1423, with two additional faint visual companions designated WDS J17146+1423C and D.[11] The two fainter stars are far more distant than the triple system.[12]

Nomenclature

α Herculis (Latinised to Alpha Herculis) is the system's Bayer designation; α1 and α2 Herculis, those of its two visible components. 64 Herculis is the system's Flamsteed designation. WDS J17146+1423 is the wider system's designation in the Washington Double Star Catalog. The designations of Alpha Herculis' main components as Alpha Herculis A and B and the wider system's four components as WDS J17146+1423A, B, C and D, together with the spectroscopic pair - Alpha Herculis Ba and Bb - derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[13]

Alpha Herculis bore the traditional name Rasalgethi or Ras Algethi (Template:Langx 'Head of the Kneeler').[14] 'Head' comes from the fact that in antiquity Hercules was depicted upside down on maps of the constellation. In 2016, the IAU organized a Working Group on Star Names (WGSN)[15] to catalog and standardize proper names for stars. The WGSN approved the name Rasalgethi for the component Alpha Herculis A (α1) on 30 June 2016 and it is now so included in the List of IAU-approved Star Names.[15]

The term ra's al-jaθiyy or Ras al Djathi appeared in the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, which was translated into Latin as Caput Ingeniculi.[16]

In Chinese astronomy, Alpha Herculis is called 帝座, Pinyin: Dìzuò, meaning 'Emperor's Seat'. The star is seen as marking itself, and stands alone in the center of the Emperor's Seat asterism, Heavenly Market enclosure (see: Chinese constellations).[17] 帝座 (Dìzuò) was westernized into Ti Tso by R.H. Allen, with the same meaning [18]

Properties

File:AlphaHerLightCurve.png
A light curve for Alpha Herculis A, plotted from data published by Wasatonic (1997)[19]

Alpha Herculis A and B are more than 500 AU apart, with an estimated orbital period of approximately 3600 years.Script error: No such module "Unsubst". A presents as a relatively massive red bright giant, but radial velocity measurements suggest a companion with a period of the order of a decade.[11] B's two components are a primary yellow giant star and a secondary, yellow-white dwarf star in a 51.578 day orbit.[20]

Alpha Herculis A is an asymptotic giant branch (AGB) star, a luminous red giant that has both hydrogen and helium shells around a degenerate carbon-oxygen core. It is the second nearest AGB star to the Sun. Its radius pulsates between 264 and 303 solar radii. At its minimum, the effective temperature is of Template:Convert and the luminosity is of 7,200 solar luminosities, while at its maximum the temperature is of Template:Convert and the luminosity is of 9,330 solar luminosities.[3] If Alpha Herculis were at the center of the Solar System its radius would extend past the orbit of Earth at 1.23Template:Snd1.4 AU but not quite as far as the orbit of Mars or the asteroid belt. The red giant is estimated to have started its life with about Template:Solar mass.[3]

The primary has been specified as a standard star for the spectral class M5 Ib-II.[3] Like most type M stars near the end of their lives, Alpha Herculis is experiencing a high degree of stellar mass loss creating a sparse, gaseous envelope that extends at least 930 AU.[20] It is a semiregular variable with complex changes in brightness with periods ranging from a few weeks to many years. The most noticeable variations occur at timescales of 80–140 days and at 1,000 - 3,000 days. The strongest detectable period is 128 days.[21] The full range in brightness is from magnitude 2.7 to 4.0,[2] but it usually varies over a much smaller range of around 0.6 magnitudes.[21]

References

Template:Reflist

External links

Template:Sky Template:Stars of Hercules Template:Portal bar

  1. ↑ a b c d e f Cite error: Invalid <ref> tag; no text was provided for refs named tycho2
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  3. ↑ a b c d e f g h i j k l m n o p q Cite error: Invalid <ref> tag; no text was provided for refs named moravveji
  4. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named ducati
  5. ↑ a b c Cite error: Invalid <ref> tag; no text was provided for refs named LEEUWEN
  6. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named huang
  7. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named reimers
  8. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named moravveji2011
  9. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named aaa465_2_593
  10. ↑ Template:Cite simbad
  11. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named WDS
  12. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named dr2cd
  13. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named planetnaming
  14. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named BBC1
  15. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named WGSN
  16. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Knobel
  17. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named aeea
  18. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named RHA
  19. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Wasatonic
  20. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named deutsch
  21. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named percy
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