Epsilon Boötis

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Template:Short description Template:About-distinguish

ε Boötis
Template:Location mark
Location of ε Boötis (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Boötes[1]
Right ascension Template:RA[2]
Declination Template:DEC[2]
Apparent magnitude (V) 2.45[3]/4.8[4]
Characteristics
Evolutionary stage red giant branch[5]
Spectral type K0 II-III[6] + A2 V[7]
U−B Template:Engvar +0.73[8]
B−V Template:Engvar +0.97[8]
Astrometry
Radial velocity (Rv)−16.31[9] km/s
Proper motion (μ) RA: −50.818 mas/yr[2]
Dec.: +21.024 mas/yr[2]
Parallax (π)13.8267±0.4896 mas[2]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)−1.61[1]
Details
A
Mass4.6[10] Template:Solar mass
RadiusScript error: No such module "val".[11] Template:Solar radius
LuminosityScript error: No such module "val".[11] Template:Solar luminosity
Surface gravity (log g)2.24[11] cgs
TemperatureScript error: No such module "val".[11] K
Metallicity [Fe/H]−0.13[9] dex
Rotational velocity (v sin i)10.9[9] km/s
B
Mass2.27[12] Template:Solar mass
Radius2.7[12] Template:Solar radius
Luminosity44.8[12] Template:Solar luminosity
Surface gravity (log g)3.9[12] cgs
Temperature9,009[12] K
Metallicity [Fe/H]−0.20[13] dex
Rotational velocity (v sin i)123[14] km/s
Other designations
Template:Odlist[15]
A: Template:Odlist[16]
B: Template:Odlist[17]
Database references
SIMBADEpsilon Boo A
Epsilon Boo B

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Epsilon Boötis is a binary star system in the northern constellation of Boötes. Its name is a Bayer designation that is Latinized from ε Boötis, and abbreviated Epsilon Boo or ε Boo. The primary component has the official name Izar, pronounced Template:IPAc-en (Script error: No such module "Respell".).[18] The star system can be viewed with the unaided eye at night, but resolving the pair with a small telescope is challenging; an aperture of Script error: No such module "convert". or greater is required.[19] Based on parallax measurements, it is located at a distance of Script error: No such module "convert".. The system is drifting closer to the Sun with a radial velocity of −16 km/s.[9]

Nomenclature

ε Boötis (Latinised to Epsilon Boötis) is the star's Bayer designation.

It bore the traditional names Izar, Mirak and Mizar, and was named Script error: No such module "Lang". Template:IPAc-en by Friedrich Georg Wilhelm von Struve.[20] Izar, and Mizar are from the Template:Langx Script error: No such module "Lang". and مئزر Mi'zar ('kilt like undergarment') and Script error: No such module "Lang". Script error: No such module "Lang". ('the loins'); Script error: No such module "Lang". is Latin for 'loveliest'.[21] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[22] to catalogue and standardize proper names for stars. The WGSN approved the name Izar for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.[18]

In the catalogue of stars in the Calendarium of Al Achsasi Al Mouakket, this star was designated Script error: No such module "Lang". (Script error: No such module "Lang". Script error: No such module "Lang".), which was translated into Latin as Script error: No such module "Lang"., meaning 'belt of barker'.[23]

In Chinese astronomy, Script error: No such module "Lang". Script error: No such module "Lang". ('Celestial Lance'), refers to an asterism consisting of Epsilon Boötis, Sigma Boötis and Rho Boötis.[24] Consequently, the Chinese name for Epsilon Boötis itself is Script error: No such module "Lang". Script error: No such module "Lang". ('the First Star of Celestial Lance').[25]

Properties

Epsilon Boötis consists of a pair of stars with an angular separation of 2.852 ± 0.014 arcseconds at a position angle of Script error: No such module "val"..[26] The brighter component (A) has an apparent visual magnitude of 2.45,[3] making it readily visible to the naked eye at night. The fainter component (B) is at magnitude 4.8,[4] which by itself would also be visible to the naked eye. Parallax measurements from the Hipparcos astrometry satellite[27][28] put the system at a distance of about Script error: No such module "convert". from the Earth.[29] This means the pair has a projected separation of 185 Astronomical Units, and they orbit each other with a period of at least 1,000 years.[21]

The brighter member has a stellar classification of K0 II-III,[6] which means it is a fairly late-stage star well into its stellar evolution, having already exhausted its supply of hydrogen fuel at the core. Evolutionary models suggest it is on the red giant branch, where hydrogen is being fused in a shell around a helium core.[5] With more than four times the mass of the Sun,[10] it has expanded to about 38 times the Sun's radius and is emitting 650 times the luminosity of the Sun. This energy is being radiated from its outer envelope at an effective temperature of Script error: No such module "val".,[11] giving it the orange hue of a K-type star.[30]

The companion star has a classification of A2 V,[7] so it is a main sequence star that is generating energy through the thermonuclear fusion of hydrogen at its core. This star is rotating rapidly, with a projected rotational velocity of Script error: No such module "val"..[14] It has a surface temperature of about Script error: No such module "val". and a radius nearly three times the Sun, leading to a bolometric luminosity 45 times that of the Sun.

Epsilon Boötis may turn out to be a quadruple system. A widely-separated brown dwarf appears to have similar proper motions with the inner pair, and thus astronomers believe both bodies may be gravitationally related. The estimated separation is of 4,900 astronomical units, but this is actually a projected separation, thus a lower limit. In addition, there is another proper motion companion at a much wider projected separation of 186,000 AU.[31]

By the time the smaller main sequence star reaches the current point of the primary in its evolution, the larger star will have lost much of its mass in a planetary nebula and will have evolved into a white dwarf. The pair will have essentially changed roles: the brighter star becoming the dim dwarf, while the lesser companion will shine as a giant star.[21]

In culture

In 1973, the Scottish astronomer and science fiction writer Duncan Lunan claimed to have managed to interpret a message caught in the 1920s by two Norwegian physicists[32] that, according to his theory, came from a 13,000 year old satellite polar orbiting the Earth known as the Black Knight and sent there by the inhabitants of a planet orbiting Epsilon Boötis.[33] The story was even reported in Time magazine.[34] Lunan later withdrew his Epsilon Boötis theory, presenting proofs against it and clarifying why he was brought to formulate it in the first place, but later revoked his withdrawal.[35]

Gallery

References

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  1. ↑ a b Template:Cite XHIP
  2. ↑ a b c d Template:Cite Gaia DR3
  3. ↑ a b Script error: No such module "Citation/CS1".
  4. ↑ a b Script error: No such module "Citation/CS1".
  5. ↑ a b 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".
  8. ↑ a b Script error: No such module "Citation/CS1".
  9. ↑ a b c d Script error: No such module "Citation/CS1".
  10. ↑ a b Script error: No such module "Citation/CS1".
  11. ↑ a b c d e Script error: No such module "Citation/CS1".
  12. ↑ a b c d e Script error: No such module "Citation/CS1".
  13. ↑ Script error: No such module "Citation/CS1".
  14. ↑ a b Script error: No such module "Citation/CS1".
  15. ↑ Template:Cite simbad
  16. ↑ Template:Cite simbad
  17. ↑ Template:Cite simbad
  18. ↑ a b Script error: No such module "citation/CS1".
  19. ↑ Script error: No such module "citation/CS1".
  20. ↑ Burnham's Celestial Handbook, Vol. 1, publ. Dover Publications, Inc., 1978
  21. ↑ a b c Script error: No such module "citation/CS1".
  22. ↑ Script error: No such module "citation/CS1".
  23. ↑ Script error: No such module "Citation/CS1".
  24. ↑ Script error: No such module "citation/CS1".
  25. ↑ Script error: No such module "citation/CS1".
  26. ↑ Script error: No such module "Citation/CS1".
  27. ↑ Script error: No such module "Citation/CS1".
  28. ↑ Script error: No such module "citation/CS1".
  29. ↑ Script error: No such module "Citation/CS1".
  30. ↑ Script error: No such module "citation/CS1".
  31. ↑ Script error: No such module "Citation/CS1".
  32. ↑ Script error: No such module "citation/CS1".
  33. ↑ Script error: No such module "Citation/CS1".
  34. ↑ Script error: No such module "Citation/CS1".
  35. ↑ Script error: No such module "Citation/CS1".

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External links

Template:Stars of Boötes

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