Shichōsei: Difference between revisions
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With normal eyesight one can make out a faint binary system just to the east of [[wikipedia:Mizar|Mizar]], the second star from the end of the [[Hokuto Shichi Sei|Big Dipper]]'s handle, named '''Alcor''' or '''80 Ursae Majoris'''. Alcor is of magnitude 3.99 and spectral class A5V. Mizar and Alcor together are sometimes called the "[[wikipedia:Horse and Rider|Horse and Rider]]," and the ability to resolve the two stars with the naked eye is often quoted as a test of eyesight, although even people with quite poor eyesight can see the two stars. Arabic literature says that only those with the sharpest eyesight can see the companion of Mizar. Astronomer Sir Patrick Moore has suggested that this in fact refers to another star which lies visually between Mizar and Alcor. Mizar and Alcor lie three [[wikipedia:light year|light-years]] apart, and though their [[wikipedia:proper motion|proper motion]]s show they move together (they are both members of the [[wikipedia:Ursa Major Moving Group|Ursa Major Moving Group]]), it was long believed they do not form a true [[wikipedia:binary star|binary star]] system, but simply a [[double star]]. However, in 2009, it was reported by astronomer Eric Mamajek and collaborators that Alcor actually is itself a binary, consisting of Alcor A and [[wikipedia:Alcor B|Alcor B]], and that this binary system is most likely gravitationally bound to Mizar, bringing the full count of stars in this complex system to six.<ref>[http://www.sciencedaily.com/releases/2009/12/091210092005.htm First Known Binary Star Is Discovered to Be a Triplet, Quadruplet, Quintuplet, Sextuplet System]</ref> Their study also demonstrated that the Alcor binary and Mizar quadruple are much closer together than previously thought - approximately 74,000 ± 39,000 [[wikipedia:Astronomical Units|Astronomical Units]].<ref>[http://adsabs.harvard.edu/abs/2009arXiv0911.5028M Discovery of a Faint Companion to Alcor Using MMT/AO 5 μm Imaging]</ref> | With normal eyesight one can make out a faint binary system just to the east of [[wikipedia:Mizar|Mizar]], the second star from the end of the [[Hokuto Shichi Sei|Big Dipper]]'s handle, named '''Alcor''' or '''80 Ursae Majoris'''. Alcor is of magnitude 3.99 and spectral class A5V. Mizar and Alcor together are sometimes called the "[[wikipedia:Horse and Rider|Horse and Rider]]," and the ability to resolve the two stars with the naked eye is often quoted as a test of eyesight, although even people with quite poor eyesight can see the two stars. Arabic literature says that only those with the sharpest eyesight can see the companion of Mizar. Astronomer Sir Patrick Moore has suggested that this in fact refers to another star which lies visually between Mizar and Alcor. Mizar and Alcor lie three [[wikipedia:light year|light-years]] apart, and though their [[wikipedia:proper motion|proper motion]]s show they move together (they are both members of the [[wikipedia:Ursa Major Moving Group|Ursa Major Moving Group]]), it was long believed they do not form a true [[wikipedia:binary star|binary star]] system, but simply a [[wikipedia:double star|double star]]. However, in 2009, it was reported by astronomer Eric Mamajek and collaborators that Alcor actually is itself a binary, consisting of Alcor A and [[wikipedia:Alcor B|Alcor B]], and that this binary system is most likely gravitationally bound to Mizar, bringing the full count of stars in this complex system to six.<ref>[http://www.sciencedaily.com/releases/2009/12/091210092005.htm First Known Binary Star Is Discovered to Be a Triplet, Quadruplet, Quintuplet, Sextuplet System]</ref> Their study also demonstrated that the Alcor binary and Mizar quadruple are much closer together than previously thought - approximately 74,000 ± 39,000 [[wikipedia:Astronomical Units|Astronomical Units]].<ref>[http://adsabs.harvard.edu/abs/2009arXiv0911.5028M Discovery of a Faint Companion to Alcor Using MMT/AO 5 μm Imaging]</ref> | ||
The whole four-star system lies about 78 light-years away from Earth. The components are all members of the [[wikipedia:Ursa Major moving group|Ursa Major moving group]], a mostly dispersed group of stars sharing a common birth, as determined by proper motion. The other stars of the Big Dipper, except [[wikipedia:Alpha Ursae Majoris|Dubhe]] and [[wikipedia:Eta Ursae Majoris|Alkaid]], belong to this group as well. | The whole four-star system lies about 78 light-years away from Earth. The components are all members of the [[wikipedia:Ursa Major moving group|Ursa Major moving group]], a mostly dispersed group of stars sharing a common birth, as determined by proper motion. The other stars of the Big Dipper, except [[wikipedia:Alpha Ursae Majoris|Dubhe]] and [[wikipedia:Eta Ursae Majoris|Alkaid]], belong to this group as well. | ||
Revision as of 19:29, 10 June 2010
 Mizar and Alcor in constellation Ursa Major.
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History
In Japanese mythology, Alcor is known as the lifespan star or "jumyouboshi" （寿命星）as it was believed that one who could not see this star would pass away by year's end. Of incidental note, the popular Japanese manga, Hokuto no Ken, used this legend as a model for its death omen star (死兆星), in which it was said that people who saw the star would die later in the year.
Star
With normal eyesight one can make out a faint binary system just to the east of Mizar, the second star from the end of the Big Dipper's handle, named Alcor or 80 Ursae Majoris. Alcor is of magnitude 3.99 and spectral class A5V. Mizar and Alcor together are sometimes called the "Horse and Rider," and the ability to resolve the two stars with the naked eye is often quoted as a test of eyesight, although even people with quite poor eyesight can see the two stars. Arabic literature says that only those with the sharpest eyesight can see the companion of Mizar. Astronomer Sir Patrick Moore has suggested that this in fact refers to another star which lies visually between Mizar and Alcor. Mizar and Alcor lie three light-years apart, and though their proper motions show they move together (they are both members of the Ursa Major Moving Group), it was long believed they do not form a true binary star system, but simply a double star. However, in 2009, it was reported by astronomer Eric Mamajek and collaborators that Alcor actually is itself a binary, consisting of Alcor A and Alcor B, and that this binary system is most likely gravitationally bound to Mizar, bringing the full count of stars in this complex system to six.[1] Their study also demonstrated that the Alcor binary and Mizar quadruple are much closer together than previously thought - approximately 74,000 ± 39,000 Astronomical Units.[2]
The whole four-star system lies about 78 light-years away from Earth. The components are all members of the Ursa Major moving group, a mostly dispersed group of stars sharing a common birth, as determined by proper motion. The other stars of the Big Dipper, except Dubhe and Alkaid, belong to this group as well.
See also
References
External links
- Alcor article at Jim Kaler's Stars website
- Shichōsei on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images