Mizar and Alcor

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Mizar (upper center) and Alcor (lower left) ALCOR et MIZAR (7060991417).jpg
Mizar (upper center) and Alcor (lower left)

Mizar and Alcor are two stars forming a naked eye double in the handle of the Big Dipper (or Plough) asterism in the constellation of Ursa Major. Their magnitudes are 2.2 and 3.9, and the pair can easily be seen without the aid of a telescope. Mizar's star is not a double star, but a four-star binary system located in the constellation Ursa Major (also known as the Big Dipper). This system consists of two pairs of double stars that are gravitationally bound to each other. Mizar is the second star from the end of the Big Dipper's handle, and Alcor its fainter companion. The traditional name Mizar derives from the Arabic المئزر or miʼzar, meaning "apron; wrapper, covering, cover". Alcor was originally the Arabic سها or Suhā/Sohā, meaning either the "forgotten" or "neglected" one; notable as a faintly perceptible companion of Mizar. [1] The ancient Persians and the Bedouins used distinguishing Mizar and Alcor as a test of vision. [2]

Contents

Mizar, also designated Zeta Ursae Majoris (ζ Ursae Majoris, abbreviated Zeta UMa, ζ UMa), is itself a quadruple system and Alcor, also designated 80 Ursae Majoris (80 UMa), is a binary, the pair together forming a sextuple system. In fact, Mizar was the first known binary star system, claimed to be discovered by Italian astronomer Giovanni Battista Riccioli in 1650. The whole system lies about 83 light-years away from the Sun, as measured by the Hipparcos astrometry satellite. [3] [4] [5]

Appearance

Mizar and Alcor in constellation Ursa Major Dipper.jpg
Mizar and Alcor in constellation Ursa Major

With normal eyesight Alcor appears at about 12 minutes of arc from Mizar. Alcor is of magnitude 3.99 and spectral class A5V. It has a faint red dwarf companion separated by 1 second of arc. [6]

Stellar system

Mizar and Alcor's proper motions show they move together, along with most of the other stars of the Big Dipper except Alpha Ursae Majoris and Eta Ursae Majoris, as members of the Ursa Major Moving Group, a mostly dispersed group of stars sharing a common birth. However, it has yet to be demonstrated conclusively that they are gravitationally bound. Gaia parallax measurements indicate that the Alcor binary and Mizar quadruple are somewhat closer together than previously thought: 0.36±0.19  pc . The uncertainty is due to no-one knowing exactly how far away the stars are. If they are exactly the same distance from us then the distance between them is only 17800 AU (0.281 ly). [7]

Between Mizar and Alcor, the 8th-magnitude star Sidus Ludoviciana is a distant background object.

Other names

Mizar is known as Vasishtha, one of the Saptarishi, and Alcor as Arundhati, wife of Vasishtha, in Indian astronomy. [8] As a married couple, they are considered to symbolize marriage and in some Hindu communities to this day priests conducting a wedding ceremony allude to or point out the asterism as a symbol of the closeness marriage brings to a couple. [9]

Although the statement has been made that Alcor was not known to the ancient Greeks, there is an old story that it was the lost Pleiad Electra, which had wandered here from her companions and became Alopex, the Fox. A Latin title was Eques Stellula, the Little Starry Horseman; Eques, the Cavalier, is from the 17th-century German astronomer Bayer. Mizar and Alcor together are sometimes called the "Horse and Rider" (and popularly, in England, Jack on the Middle Horse), with Mizar being the horse. [1] The Persian astronomer Al Biruni (973–1048 AD) mentioned its importance in the family life of the Arabs on the 18th day of the Syrian month Adar, the March equinox; and a modern story of that same people makes it the infant of the walidan (mother?) among the three Banat (the Mourners: Alioth, Mizar, and Alkaid).[ citation needed ]

Chinese Taoism personifies ζ Ursae Majoris as the Lu star.[ citation needed ]

In Chinese, 北斗 (Běi Dǒu), meaning Northern Dipper , refers to an asterism consisting of Zeta Ursae Majoris, Alpha Ursae Majoris, Beta Ursae Majoris, Gamma Ursae Majoris, Delta Ursae Majoris, Epsilon Ursae Majoris and Eta Ursae Majoris. Consequently, Zeta Ursae Majoris itself is known as 北斗六 Běi Dǒu liù, (English: the Sixth Star of Northern Dipper) and 開陽 Kāi Yáng, (English: Star of The Opener of Heat). [10]

Mizar is Chickadee and Alcor is his cooking pot in the Mi'kmaq myth of the great bear and the seven hunters. [11]

Test of eyesight

The ability to resolve Mizar and Alcor with the naked eye is often quoted as a test of eyesight and that has been confirmed by modern experimental research. [12] Arabic literature says that only those with the sharpest eyesight can see the companion of Mizar. The 14th century Arabian lexicographer Firuzabadi called it "Our Riddle", while the 13th century Persian astronomical writer Zakariya al-Qazwini said that "people tested their eyesight by this star." In Japan, Alcor is sometimes referred to as the "Lifespan Star" 寿命星 (Jumyōboshi), and it was rumoured that being unable to see Alcor with the naked eye was a sign of impending death from old age. [13] [14]

Humboldt wrote of it as being seen with difficulty, and Arago similarly alluded to it. Astronomer Patrick Moore suggested that this in fact refers to another star that lies visually between Mizar and Alcor. [15] This star is occasionally known as "Ludwig's Star", because it was observed on 2 December 1722 by the German astronomer Johann Georg Liebknecht and named in honour of his patron the Landgrave Ludwig of Hessen-Darmstadt. [16] Liebknecht thought it was a planet, but it had already been observed in exactly the same position by Benedetto Castelli approximately a century earlier, which indicated it was a background star.

Agnes M. Clerke wrote:

"The Arabs in the desert regarded it as a test of penetrating vision; and they were accustomed to oppose "Sohail" to "Soha" (Canopus to Alcor) as occupying respectively the highest and lowest posts in the celestial hierarchy. So that Vidit Alcor, at non lunam plenam (Latin for "he saw Alcor, but not the full moon"), came to be a proverbial description of one keenly alive to trifles, but dull of apprehension for broad facts." [17]

6-star system

Benedetto Castelli, one of Galileo's colleagues in the 17th century, observed Mizar through a telescope and realized that it was a binary system: Mizar A and Mizar B. Then, throughout the 19th century and the beginning of the 20th century, with the help of spectroscopy, scientists showed that Mizar A and B were both binary systems. In 1908, the Alcor-Mizar system was the first apparent 5-star system ever discovered.

In 2009, Eric Mamajek and his colleagues from the University of Rochester, while searching for exoplanets, discovered that Alcor was also a binary system, making Alcor and Mizar a 6-star system. The same conclusion was independently found by Ben Oppenheimer from the American Natural History Museum. [6]

See also

Related Research Articles

<span class="mw-page-title-main">Alioth</span> Star in the constellation Ursa Major

Alioth, also called Epsilon Ursae Majoris, is a star in the northern constellation of Ursa Major. The designation is Latinised from ε Ursae Majoris and abbreviated Epsilon UMa or ε UMa. Despite being designated "ε" (epsilon), it is the brightest star in the constellation and at magnitude 1.77 is the thirty-third brightest star in the sky.

<span class="mw-page-title-main">Ursa Major</span> Constellation in the northern sky

Ursa Major, also known as the Great Bear, is a constellation in the northern sky, whose associated mythology likely dates back into prehistory. Its Latin name means "greater bear", referring to and contrasting it with nearby Ursa Minor, the lesser bear. In antiquity, it was one of the original 48 constellations listed by Ptolemy in the 2nd century AD, drawing on earlier works by Greek, Egyptian, Babylonian, and Assyrian astronomers. Today it is the third largest of the 88 modern constellations.

<span class="mw-page-title-main">Ursa Minor</span> Constellation in the northern celestial hemisphere

Ursa Minor, also known as the Little Bear, is a constellation located in the far northern sky. As with the Great Bear, the tail of the Little Bear may also be seen as the handle of a ladle, hence the North American name, Little Dipper: seven stars with four in its bowl like its partner the Big Dipper. Ursa Minor was one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and remains one of the 88 modern constellations. Ursa Minor has traditionally been important for navigation, particularly by mariners, because of Polaris being the north pole star.

<span class="mw-page-title-main">Beta Ursae Minoris</span> Star in the constellation Ursa Minor

Kochab, Bayer designation Beta Ursae Minoris, is the brightest star in the bowl of the Little Dipper asterism, and only slightly fainter than Polaris, the northern pole star and brightest star in Ursa Minor. Kochab is 16 degrees from Polaris and has an apparent visual magnitude of 2.08. The distance to this star from the Sun can be deduced from the parallax measurements made during the Hipparcos mission, yielding a value of 130.9 light-years.

<span class="mw-page-title-main">Phecda</span> Star in the constellation Ursa Major

Phecda, also called Gamma Ursae Majoris, is a star in the constellation of Ursa Major. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. Based upon parallax measurements with the Hipparcos astrometry satellite, it is located at a distance of around 83.2 light-years from the Sun.

<span class="mw-page-title-main">Asterism (astronomy)</span> Pattern of stars recognized on Earths night sky

An asterism is an observed pattern or group of stars in the sky. Asterisms can be any identified pattern or group of stars, and therefore are a more general concept than the 88 formally defined constellations. Constellations are based on asterisms, but unlike asterisms, constellations outline and today completely divide the sky and all its celestial objects into regions around their central asterisms. For example, the asterism known as the Big Dipper or the Plough comprises the seven brightest stars in the constellation Ursa Major. Another asterism is the triangle, within the constellation of Capricornus.

<span class="mw-page-title-main">Dubhe</span> Binary star in the constellation Ursa Major

Dubhe is a multiple star system in the northern constellation of Ursa Major. It is formally designated Alpha Ursae Majoris, Latinised from α Ursae Majoris, Despite being designated "α" (alpha), it is the second-brightest object in the constellation. Alpha Ursae Majoris is the northern of the 'pointers', the second being Beta Ursae Majoris, or 'Merak' – this pair of stars point towards Polaris, the North Star. α Ursae Majoris is located at a distance of approximately 123 light years from the Sun, based on parallax measurements.

<span class="mw-page-title-main">Merak (star)</span> Star in the constellation Ursa Major

Merak, also called Beta Ursae Majoris, is a star in the northern constellation of Ursa Major.

<span class="mw-page-title-main">Alkaid</span> Star in the constellation Ursa Major

Alkaid, also called Eta Ursae Majoris, is a star in the constellation of Ursa Major. It is the most eastern (leftmost) star in the Big Dipper asterism. However, unlike most stars of the Big Dipper, it is not a member of the Ursa Major moving group. With an apparent visual magnitude of +1.86, it is the third-brightest star in the constellation and one of the brightest stars in the night sky.

<span class="mw-page-title-main">Alcor (star)</span> Star in the constellation of Ursa Major

Alcor is a binary star system in the constellation of Ursa Major. It is the fainter companion of Mizar, the two stars forming a naked eye double in the handle of the Big Dipper asterism in Ursa Major. The two lie about 83 light-years away from the Sun, as measured by the Hipparcos astrometry satellite.

<span class="mw-page-title-main">Mizar</span> Quadruple star system in Ursa Major

Mizar is a second-magnitude star in the handle of the Big Dipper asterism in the constellation of Ursa Major. It has the Bayer designation ζ Ursae Majoris. It forms a well-known naked eye double star with the fainter star Alcor, and is itself a quadruple star system. The Mizar and Alcor system lies about 83 light-years away from the Sun, as measured by the Hipparcos astrometry satellite, and is part of the Ursa Major Moving Group.

Megrez, also called Delta Ursae Majoris, is a star in the northern constellation of Ursa Major. With an apparent magnitude of +3.3, it is the dimmest of the seven stars in the Big Dipper asterism. Parallax measurements yield a distance estimate of 80.5 light-years from the Sun.

Mu Ursae Majoris, formally named Tania Australis, is a binary star in the constellation of Ursa Major. An apparent visual magnitude of +3.06 places it among the brighter members of the constellation. Parallax measurements give an estimated distance of roughly 230 light-years from the Sun, with a margin of error of 4%.

Iota Ursae Majoris, also named Talitha, is a star system in the northern circumpolar constellation of Ursa Major. It has an apparent visual magnitude of 3.14, making it visible to the naked eye and placing it among the brighter members of this constellation. Based upon parallax measurements, it is located at a distance of 47.3 light-years from the Sun.

Xi Ursae Majoris is a quintuple star system 28.5 light-years away in the constellation of Ursa Major. It has the traditional name Alula Australis; Xi Ursae Majoris is the Bayer designation, which is Latinised from ξ Ursae Majoris and abbreviated Xi UMa or ξ UMa. It was the first visual double star for which an orbit was calculated, when it was computed by Félix Savary in 1828. It is also a variable star with a small amplitude. Xi Ursae Majoris is found in the left hind paw of the Great Bear.

<span class="mw-page-title-main">Zeta Ursae Minoris</span> Star in the constellation Ursa Minor

Zeta Ursae Minoris, which is Latinized from ζ Ursae Minoris, is a single star in the northern circumpolar constellation of Ursa Minor, forming the northernmost part of the bowl in this "little dipper" asterism. The star has a white hue and is faintly visible to the naked eye with an apparent visual magnitude of +4.28. It is located at a distance of approximately 369 light-years from the Sun based on parallax, but is drifting further closer with a radial velocity of about –13 km/s.

<span class="mw-page-title-main">Saptarshi</span> Seven sages of Hinduism

The Saptarshi are the seven seers of ancient India who are extolled in the Vedas, and other Hindu literature such as the Skanda Purana. The Vedic Samhitas never enumerate these rishis by name, although later Vedic texts such as the Brahmanas and Upanisads do so these constellations are easily recognizable.

<span class="mw-page-title-main">Big Dipper</span> Pattern of seven bright stars in the constellation Ursa Major

The Big Dipper or the Plough is a large asterism consisting of seven bright stars of the constellation Ursa Major; six of them are of second magnitude and one, Megrez (δ), of third magnitude. Four define a "bowl" or "body" and three define a "handle" or "head". It is recognized as a distinct grouping in many cultures. The North Star (Polaris), the current northern pole star and the tip of the handle of the Little Dipper, can be located by extending an imaginary line through the front two stars of the asterism, Merak (β) and Dubhe (α). This makes it useful in celestial navigation.

Sigma2 Ursae Majoris is a binary star in the constellation of Ursa Major. Parallax measurements made by the Hipparcos spacecraft put it at a distance of about 66.5 light years from Earth, making this a fairly nearby system. The primary component has an apparent magnitude of about 4.8, meaning it can be seen with the naked eye (see Bortle scale).

<span class="mw-page-title-main">Sidus Ludoviciana</span> Star in the constellation Ursa Major

Sidus Ludoviciana, also known as HD 116798 is an 8th-magnitude giant star in the asterism of the Big Dipper in the constellation Ursa Major, halfway between Mizar and Alcor. It was discovered on 2 December 1722 by Johann Georg Liebknecht, who mistook it for a planet and named it after Louis V, Landgrave of Hesse-Darmstadt. A line-of-sight companion with Mizar and Alcor, it is roughly four times more distant. It has the spectral type A8/F0 III. That spectral class suggests it is a giant star, but evolutionary models place it on the main sequence.

References

  1. 1 2 "Star Tales – Mizar and Alcor" . Retrieved 2024-07-22.
  2. ↑ Bohigian, George M. (September 2008). "An Ancient Eye Test—Using the Stars". Survey of Ophthalmology. 53 (5): 536–539. doi:10.1016/j.survophthal.2008.06.009.
  3. ↑ van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv: 0708.1752 . Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID   18759600.
  4. ↑ Perryman, M. A. C.; Lindegren, L.; Kovalevsky, J.; Hoeg, E.; Bastian, U.; Bernacca, P. L.; Crézé, M.; Donati, F.; Grenon, M.; Grewing, M.; Van Leeuwen, F.; Van Der Marel, H.; Mignard, F.; Murray, C. A.; Le Poole, R. S.; Schrijver, H.; Turon, C.; Arenou, F.; Froeschlé, M.; Petersen, C. S. (1997). "The HIPPARCOS Catalogue". Astronomy and Astrophysics. 323: L49. Bibcode:1997A&A...323L..49P.
  5. ↑ Perryman, Michael (2010). The Making of History's Greatest Star Map. Astronomers’ Universe. Heidelberg: Springer-Verlag. Bibcode:2010mhgs.book.....P. doi:10.1007/978-3-642-11602-5. ISBN   978-3-642-11601-8.
  6. 1 2 Zimmerman, Neil; Oppenheimer, Ben R; Hinkley, Sasha; Brenner, Douglas; Parry, Ian R; Sivaramakrishnan, Anand; Hillenbrand, Lynne; Beichman, Charles; Crepp, Justin R; Vasisht, Gautam; Roberts, Lewis C; Burruss, Rick; King, David L; Soummer, Rémi; Dekany, Richard; Shao, Michael; Bouchez, Antonin; Roberts, Jennifer E; Hunt, Stephanie (2010). "Parallactic Motion for Companion Discovery: An M-Dwarf Orbiting Alcor". The Astrophysical Journal. 709 (2): 733–740. arXiv: 0912.1597 . Bibcode:2010ApJ...709..733Z. doi:10.1088/0004-637X/709/2/733. S2CID   6052794.
  7. ↑ Mamajek, Eric E.; Kenworthy, Matthew A.; Hinz, Philip M.; Meyer, Michael R. (2010). "Discovery of a Faint Companion to Alcor Using MMT/AO 5 μm Imaging". The Astronomical Journal. 139 (3): 919–925. arXiv: 0911.5028 . Bibcode:2010AJ....139..919M. doi:10.1088/0004-6256/139/3/919. S2CID   51834159.
  8. ↑ V.Chandran (1993-01-01). Astronomy Quiz Book. Pustak Mahal, 1993. ISBN   978-81-223-0366-7. ... the seven rishis in the asterism Saptarishi (Ursa Major) ... In Vasishta (Zeta), its tiny companion star is named after Arundhati, the wife of Vasishta ... today known by their Arabic names Dubhe (Kratu), Merak (Pulaha), Phekda (Pulastya), Megrez (Atri), Benetnash (Marichi) and Mizar (Vasishta) ...
  9. ↑ M.K.V. Narayan (2007-04-01). Flipside of Hindu Symbolism: Sociological and Scientific Linkages in Hinduism. Fultus Corporation, 2007. ISBN   978-1-59682-117-0. ... At this time, the pundit shows the couple the Arundhati star in the sky to suggest closeness of the married couple. ... the star Vasishta of the Big Dipper asterism (Saptarishi Mandalam) and it is the star system called Mizar ...
  10. ↑ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 15 日
  11. ↑ "The Celestial Bear, A Micmac Legend". Archived from the original on 2017-10-18. Retrieved 2014-01-07.
  12. ↑ Bohigian, George M. (2008). "An Ancient Eye Test—Using the Stars". Survey of Ophthalmology. 53 (5): 536–9. doi:10.1016/j.survophthal.2008.06.009. PMID   18929764.
  13. ↑ "Big Dipper". WFYI Public Media. Retrieved 2022-10-26.
  14. ↑ Miller, James (2017-09-07). "Star Facts: Mizar and Alcor - Star Types, Size, & Location" . Retrieved 2022-10-26.
  15. ↑ Moore, Patrick; Watson, John (2012). "Observing the Stars and Galaxies". Astronomy with a Budget Telescope. Patrick Moore's Practical Astronomy Series. p. 65. doi:10.1007/978-1-4614-2161-0_5. ISBN   978-1-4614-2160-3.
  16. ↑ "Big Dipper Stars in Summer Sky". Space.com . Retrieved 2017-03-03.
  17. ↑ Clerke, Agnes Mary (1901). The Herschels and Modern Astronomy. The Century Science Series. London: Cassell and Company. p.  82. OCLC   4530404.
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