Capella: Difference between revisions

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components generally called Aa/Ab
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===Capella's comparative luminosity===
===Capella's comparative luminosity===
Comparing Capella to the nearest bright star, [[Alpha Centauri]], Capella is of similar [[visual magnitude]] yet it is around 10 times further away. Since the [[intensity]] of [[light]] decreases as the square of the distance, Capella is therefore around 70 times the [[luminosity]] of Alpha Centauri.
Comparing Capella to the nearest bright star, [[Alpha Centauri]], Capella is of similar [[visual magnitude]] yet it is around 10 times further away. Since the [[intensity]] of [[light]] decreases as the square of the distance, Capella is therefore around 70 times the [[luminosity]] of Alpha Centauri.
{{-}}
==Companion binary==
{{Starbox 2
| name = [[Catalog of Components of Double and Multiple Stars|CCDM]] J05168+4559HL
| epoch = [[J2000.0]]
| equinox = [[J2000.0]] ([[International Celestial Reference System|ICRS]])
| constell = [[Auriga (constellation)|Auriga]]
| ra_a_h = 05
| ra_a_m = 17
| ra_a_s = 23.728
| radec_a_footnote = <ref name=sb1>{{SIMBAD link|CCDM+J05168%2B4559H|G 96-29 -- High proper-motion Star}}, database entry, [[SIMBAD]]. Accessed on line December 23, 2008.</ref>
| dec_a_d = +45
| dec_a_m = 50
| dec_a_s = 22.97
| ra_b_h = 05
| ra_b_m = 17
| ra_b_s = 23.77
| radec_b_footnote = <ref name=sb2>{{SIMBAD link|CCDM+J05168%2B4559L|NAME CAPELLA L -- Star in double system}}, database entry, [[SIMBAD]]. Accessed on line December 23, 2008.</ref>
| dec_b_d = +45
| dec_b_m = 50
| dec_b_s = 29.0
| appmag_v_a = 10.16<ref name=sb1 />
| class_a = M1<ref name=sb1 />
| b-v_a = 1.5<ref name=sb1 />
| v-r_a = 0.5<ref name=sb1 />
| appmag_v_b = 13.7<ref name=sb2 />
| class_b = M5<ref name=sb2 />
| b-v_b = 0.3<ref name=sb2 />
| radial_v_a = 36&nbsp;±&nbsp;5<ref name=sb1 />
| prop_mo_ra_a = 58.5<ref name=sb1 />
| prop_mo_dec_a = −410.0<ref name=sb1 />
| prop_mo_ra_b = 58<ref name=sb2 />
| prop_mo_dec_b = −401<ref name=sb2 />
| parallax = 72.00
| p_error = 4.00
| parallax_footnote = <ref name=sb1 />
| absmag_v_a = 9.4<ref name=n group=note />
| absmag_v_b = 13.0<ref name=n group=note />
| orbit_footnote=<ref name=heintz75>
| period_unitless=388&nbsp;[[year|y]]
| axis_unitless=3.72[[arcsecond|″]]
| periastron=2010
| inclination=65.0
| node=168.5
| eccentricity=0
| periarg=0
| names='''HL''': Capella&nbsp;HL, [[Aitken Double Star Catalogue|ADS]]&nbsp;3841&nbsp;HL, [[Gliese-Jahreiss catalogue|GJ]]&nbsp;195&nbsp;AB.<br />'''H''': [[Luyten Two-Tenths catalogue|LTT]]&nbsp;11622, [[New Luyten Two-Tenths catalogue|NLTT]]&nbsp;14788, [[PPM Star Catalogue|PPM]]&nbsp;47938.<ref name=sb1 /><ref name=sb2 /><ref name=chl />
| simbad_a = CCDM+J05168%2B4559H
| simbad_b = CCDM+J05168%2B4559L}}
{{Starbox end}}
A [[binary star|binary system]] of red dwarfs can be observed close to the spectroscopic binary of G-type giants. The two pairs are thought to be physically bound to each other, at a distance of around 10,000 [[astronomical unit|AU]].<ref name=chl>Capella HL, T. R. Ayres, pp. 202–204, in ''Cool Stars, Stellar Systems, and the Sun: Proceedings of the Third Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, Held in Cambridge, Massachusetts, October 5-7, 1983''; edited by Sallie L. Baliunas and Lee Hartmann, Berlin/Heidelberg, Springer-Verlag, 1984, Lecture Notes in Physics, vol. 193, ISBN 978-3-540-12907-3; {{doi|10.1007/3-540-12907-3_204}}, {{bibcode|1984LNP...193..202A}}</ref> Although this pair has only been observed to cover approximately 30&deg; of its orbit, a rough, preliminary orbit has been computed, giving an orbital period of approximately 400 years.<ref name=heintz75>Parallax and motions of the Capella system, W. D. Heintz, ''Astrophysical Journal'' '''195''' (January 1975), pp. 411–412, {{doi|10.1086/153340}}, {{bibcode|1975ApJ...195..411H}}</ref>


==Etymology and cultural significance==
==Etymology and cultural significance==

Revision as of 00:40, 25 December 2008

For other uses, see Capella.

Template:Starbox 2 Capella (α Aur / α Aurigae / Alpha Aurigae) is the brightest star in the constellation Auriga and eleventh brightest star in the sky. Although it appears as a single point to the naked eye, Capella is actually a bright close binary pair of yellow giant stars alongside a second, fainter binary.

System

A yellow star, it traditionally marks the left shoulder of the constellation's eponymous charioteer, or sometimes the goat that the charioteer is carrying. It is closer to the north celestial pole than any other first magnitude star (Polaris is only second magnitude) and as a result has played a significant role in many mythological writings. A tablet dating back to 2000 BC refers to Capella.

Astronomically, Capella's interest lies in the fact that it is an easily-studied non-eclipsing spectroscopic binary star. These two giant G-class stars have luminosities of around 50 and 80 times that of the Sun and lie less than 100 million km apart with an orbital period of 104.02 days. The stars were probably of spectral class A during their main sequence, similar to Sirius, and are in the process of becoming red giants in a few million more years as they continue to expand, cool, and brighten. Capella is a source of X-rays, probably due to surface magnetic activity on one of the pair. The Capella binary was the first star system to be imaged using a long baseline optical astronomical interferometer in observations by COAST in 1995.

The central stars also have a faint companion that is itself a double star, consisting of two M-class red dwarf stars, that orbit at around a light year away from the main pair.

Capella's comparative luminosity

Comparing Capella to the nearest bright star, Alpha Centauri, Capella is of similar visual magnitude yet it is around 10 times further away. Since the intensity of light decreases as the square of the distance, Capella is therefore around 70 times the luminosity of Alpha Centauri.

Companion binary

{{Starbox 2 | name = CCDM J05168+4559HL | epoch = J2000.0 | equinox = J2000.0 (ICRS) | constell = Auriga | ra_a_h = 05 | ra_a_m = 17 | ra_a_s = 23.728 | radec_a_footnote = [1] | dec_a_d = +45 | dec_a_m = 50 | dec_a_s = 22.97 | ra_b_h = 05 | ra_b_m = 17 | ra_b_s = 23.77 | radec_b_footnote = [2] | dec_b_d = +45 | dec_b_m = 50 | dec_b_s = 29.0 | appmag_v_a = 10.16[1] | class_a = M1[1] | b-v_a = 1.5[1] | v-r_a = 0.5[1] | appmag_v_b = 13.7[2] | class_b = M5[2] | b-v_b = 0.3[2] | radial_v_a = 36 ± 5[1] | prop_mo_ra_a = 58.5[1] | prop_mo_dec_a = −410.0[1] | prop_mo_ra_b = 58[2] | prop_mo_dec_b = −401[2] | parallax = 72.00 | p_error = 4.00 | parallax_footnote = [1] | absmag_v_a = 9.4[note 1] | absmag_v_b = 13.0[note 1] | orbit_footnote=Cite error: A <ref> tag is missing the closing </ref> (see the help page). Although this pair has only been observed to cover approximately 30° of its orbit, a rough, preliminary orbit has been computed, giving an orbital period of approximately 400 years.[3]

Etymology and cultural significance

The name Capella means 'little she goat' in Latin, as in Roman mythology the star represented the goat Amalthea that suckled Jupiter. It was this goat whose horn, after accidentally being broken off by Jupiter, was transformed into the Cornucopia, or "horn of plenty", which would be filled with whatever its owner desired.

In Hindu mythology, Capella was seen as the heart of Brahma. The star is also often labelled "the shepherd's star" in English literature.

Astrologically, Capella portends civic and military honors and wealth. In the Middle Ages, it was considered a Behenian fixed star with sapphire and thyme as attributes. Cornelius Agrippa listed its kabbalistic sign with the name Hircus (Latin, "goat").

In Persian literature, Capella (Bozbān, Ayyuq) is a metaphor for a huge distance and also the light red colour.

In Australian Aboriginal mythology, Capella was Purra, the kangaroo, pursued and killed by the nearby Gemini twins or by the Orion hunter,[4][5][6] or near the Orion belt twins canoe.[7]


To the Bedouin people of the Negev and Sinai, Capella is known as al-'Ayūg, 'the dandy', in its role as pointing out the position of the Pleiades -its name more fully al-'Ayūg ath-Thurayyā 'dandy of the Pleiades'.[8]

Alternative and former names

Due to its brightness, Capella has had a name in several cultures.

  • Arabic: al-'Ayyuq العيوق (Alhajoth) ("Goat")
  • Hindu: Brahmahridaya ("Heart of Brahma")
  • Persian: Bozbān بزبان ("Goat-keeper"), Negahbān نگهبان ("Guard")
  • Inca: Colca
  • Latin: Amalthea, Hircus ("Goat")
  • Hawaiian: Hokulei ("Star-Wreath")
  • Chinese: Wǔjū'èr 五车二 ("Second Star of the Five Chariots")

See also

Notes

  1. ^ a b Cite error: The named reference n was invoked but never defined (see the help page).

References

  1. ^ a b c d e f g h i G 96-29 -- High proper-motion Star, database entry, SIMBAD. Accessed on line December 23, 2008.
  2. ^ a b c d e f NAME CAPELLA L -- Star in double system, database entry, SIMBAD. Accessed on line December 23, 2008.
  3. ^ Parallax and motions of the Capella system, W. D. Heintz, Astrophysical Journal 195 (January 1975), pp. 411–412, doi:10.1086/153340, Bibcode:1975ApJ...195..411H
  4. ^ http://www.atnf.csiro.au/research/AboriginalAstronomy/literature/Stanbridge1857.pdf
  5. ^ Australian Zodiac
  6. ^ http://www.atnf.csiro.au/people/rnorris/SydneyRockArt/sites/TerreyHillsHunt/mosaic.jpg
  7. ^ http://www.brandlehner.at/Brandlehner/c2picture.nsf/pictures/CBRR-6FGLDF/$File/CBRR-6FGLDF.jpg
  8. ^ Bailey, Clinton (1974). (abstract) "Bedouin Star-Lore in Sinai and the Negev" (abstract). Bulletin of the School of Oriental and African Studies, University of London. 37 (3): 580–96. Retrieved 2008-01-14. {{cite journal}}: Check |url= value (help)
  • Hummel, C. A., et al., 1994, AJ, 107, 1859
  • Fact and Fancy {Intriguing Speculations on the Possibilities of Science} by Isaac Asimov, Discus/Avon Books, March 1972, pages 152-155.

External links


Template:Binary-star-stub

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