HOME

TheInfoList



OR:

Mizar and Alcor are two stars forming a
naked eye Naked eye, also called bare eye or unaided eye, is the practice of engaging in visual perception unaided by a magnification, magnifying, Optical telescope#Light-gathering power, light-collecting optical instrument, such as a telescope or microsc ...
double Double, The Double or Dubble may refer to: Mathematics and computing * Multiplication by 2 * Double precision, a floating-point representation of numbers that is typically 64 bits in length * A double number of the form x+yj, where j^2=+1 * A ...
in the handle of the
Big Dipper The Big Dipper (American English, US, Canadian English, Canada) or the Plough (British English, UK, Hiberno-English, Ireland) is an asterism (astronomy), asterism consisting of seven bright stars of the constellation Ursa Major; six of them ar ...
(or Plough) asterism in the
constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...
of
Ursa Major 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 (or larger) bear", referring to and contrasting it with nearby Ursa M ...
. Their magnitudes are 2.2 and 3.9, and the pair can easily be seen without the aid of a telescope.
Mizar 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 ( Latinised as Zeta Ursae Majoris). It forms a well-known naked eye d ...
and its fainter companion Alcor are actually a four-star binary system consisting of two pairs of double stars that are gravitationally bound to each other. 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. The ancient Persians and the Bedouins used distinguishing Mizar and Alcor as a test of vision. 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 Binary may refer to: Science and technology Mathematics * Binary number, a representation of numbers using only two values (0 and 1) for each digit * Binary function, a function that takes two arguments * Binary operation, a mathematical op ...
, 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 The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...
, as measured by the
Hipparcos ''Hipparcos'' was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions and distances of ...
astrometry satellite.


Appearance

With normal eyesight Alcor appears at about 12
minutes of arc A minute of arc, arcminute (abbreviated as arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of a degree. Since one degree is of a turn, or complete rotation, one arcminute is of a tu ...
from Mizar. Alcor is of magnitude 3.99 and spectral class A5V. It has a faint
red dwarf A red dwarf is the smallest kind of star on the main sequence. Red dwarfs are by far the most common type of fusing star in the Milky Way, at least in the neighborhood of the Sun. However, due to their low luminosity, individual red dwarfs are ...
companion separated by 1
second of arc A minute of arc, arcminute (abbreviated as arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of a degree. Since one degree is of a turn, or complete rotation, one arcminute is of a tu ...
.


Stellar system

Mizar and Alcor's
proper motion Proper motion is the astrometric measure of changes in the apparent places of stars or other celestial objects as they move relative to the center of mass of the Solar System. It is measured relative to the distant stars or a stable referenc ...
s show they move together, along with most of the other stars of the Big Dipper except
Alpha Ursae Majoris Dubhe is a multiple star system in the northern constellation of Ursa Major. It is formally designated Alpha Ursae Majoris, Latinisation of names, Latinised from α Ursae Majoris, Despite being designated "α" (alpha), it is the sec ...
and
Eta Ursae Majoris Alkaid , also called Eta Ursae Majoris ( Latinised from η Ursae Majoris, abbreviated Eta UMa, η UMa), is a star in the constellation of Ursa Major. It is the easternmost star in the Big Dipper (or Plough) asterism. Howeve ...
, as members of the
Ursa Major Moving Group The Ursa Major Moving Group, also known as Collinder 285 and the Ursa Major association, is the closest Stellar kinematics#Moving groups, stellar moving group – a set of stars with common velocities in space and thought to have a common orig ...
, a mostly dispersed group of stars sharing a common birth. However, it has yet to be demonstrated conclusively that they are gravitationally bound.
Gaia In Greek mythology, Gaia (; , a poetic form of ('), meaning 'land' or 'earth'),, , . also spelled Gaea (), is the personification of Earth. Gaia is the ancestral mother—sometimes parthenogenic—of all life. She is the mother of Uranus (S ...
parallax measurements indicate that the Alcor binary and Mizar quadruple are somewhat closer together than previously thought: . 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 . Between Mizar and Alcor, the 8th-magnitude star Sidus Ludoviciana is a distant background object.


Other names

Mizar is known as
Vasishtha Vasishtha (, ) is one of the oldest and revered Vedic rishis or sages, and one of the Saptarishis (seven great Rishis). Vasishtha is credited as the chief author of Mandala 7 of the ''Rigveda''. Vasishtha and his family are mentioned in Rigve ...
, one of the
Saptarishi 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 Br ...
, and Alcor as Arundhati, wife of Vasishtha, in
Indian astronomy Astronomy has a long history in the Indian subcontinent, stretching from History of India, pre-historic to History of India (1947–present), modern times. Some of the earliest roots of Indian astronomy can be dated to the period of Indus Valle ...
. As a married couple, they are considered to symbolize marriage and in some
Hindu Hindus (; ; also known as Sanātanīs) are people who religiously adhere to Hinduism, also known by its endonym Sanātana Dharma. Jeffery D. Long (2007), A Vision for Hinduism, IB Tauris, , pp. 35–37 Historically, the term has also be ...
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. Although the statement has been made that Alcor was not known to the
ancient Greeks Ancient Greece () was a northeastern Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of classical antiquity (), that comprised a loose collection of culturally and linguistically re ...
, 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 Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
title was Eques Stellula, the Little Starry Horseman; Eques, the Cavalier, is from the 17th-century German astronomer
Bayer Bayer AG (English: , commonly pronounced ; ) is a German multinational pharmaceutical and biotechnology company and is one of the largest pharmaceutical companies and biomedical companies in the world. Headquartered in Leverkusen, Bayer' ...
. Mizar and Alcor together are sometimes called the "Horse and Rider" (and popularly, in
England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...
, Jack on the Middle Horse), with Mizar being the horse. The Persian astronomer Al Biruni (973–1048 AD) mentioned its importance in the family life of the
Arab Arabs (,  , ; , , ) are an ethnic group mainly inhabiting the Arab world in West Asia and North Africa. A significant Arab diaspora is present in various parts of the world. Arabs have been in the Fertile Crescent for thousands of years ...
s on the 18th day of the Syrian month
Adar Adar (Hebrew: , ; from Akkadian ''adaru'') is the sixth month of the civil year and the twelfth month of the religious year on the Hebrew calendar, roughly corresponding to the month of March in the Gregorian calendar. It is a month of 29 days. ...
, the
March equinox The March equinox or northward equinox is the equinox on the Earth when the subsolar point appears to leave the Southern Hemisphere and cross the celestial equator, heading northward as seen from Earth. The March equinox is known as the ver ...
; 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). Chinese
Taoism Taoism or Daoism (, ) is a diverse philosophical and religious tradition indigenous to China, emphasizing harmony with the Tao ( zh, p=dào, w=tao4). With a range of meaning in Chinese philosophy, translations of Tao include 'way', 'road', ' ...
personifies ζ Ursae Majoris as the Lu star. In Chinese, (), meaning '' Northern Dipper'', refers to an asterism consisting of Zeta Ursae Majoris,
Alpha Ursae Majoris Dubhe is a multiple star system in the northern constellation of Ursa Major. It is formally designated Alpha Ursae Majoris, Latinisation of names, Latinised from α Ursae Majoris, Despite being designated "α" (alpha), it is the sec ...
,
Beta Ursae Majoris Merak , also called Beta Ursae Majoris (β Ursae Majoris, abbreviated Beta UMa, β UMa), is a star in the northern constellation of Ursa Major. The apparent visual magnitude of this star is +2.37, which means it is readil ...
, Gamma Ursae Majoris, Delta Ursae Majoris, Epsilon Ursae Majoris and
Eta Ursae Majoris Alkaid , also called Eta Ursae Majoris ( Latinised from η Ursae Majoris, abbreviated Eta UMa, η UMa), is a star in the constellation of Ursa Major. It is the easternmost star in the Big Dipper (or Plough) asterism. Howeve ...
. Consequently, Zeta Ursae Majoris itself is known as Běi Dǒu liù, () and Kāi Yáng, (). Mizar is Chickadee and Alcor is his cooking pot in the
Mi'kmaq The Mi'kmaq (also ''Mi'gmaq'', ''Lnu'', ''Mi'kmaw'' or ''Mi'gmaw''; ; , and formerly Micmac) are an Indigenous group of people of the Northeastern Woodlands, native to the areas of Canada's Atlantic Provinces, primarily Nova Scotia, New Bru ...
myth of the great bear and the seven hunters.


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. Arabic literature says that only those with the sharpest eyesight can see the companion of Mizar. The 14thcentury Arabian lexicographer Firuzabadi called it "Our Riddle", while the 13thcentury Persian astronomical writer
Zakariya al-Qazwini Zakariyya' al-Qazwini ( , ), also known as Qazvini (), (born in Qazvin, Iran, and died 1283), was a Cosmography, cosmographer and Geography in medieval Islam, geographer. He belonged to a family of jurists originally descended from Anas bin Mal ...
said that "people tested their eyesight by this star." In
Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...
, Alcor is sometimes referred to as the "Lifespan Star" , and it was rumoured that being unable to see Alcor with the naked eye was a sign of impending death from old age. Humboldt wrote of it as being seen with difficulty, and Arago similarly alluded to it. Astronomer
Patrick Moore Sir Patrick Alfred Caldwell-Moore (; 4 March 1923 – 9 December 2012) was an English amateur astronomer who attained prominence in that field as a writer, researcher, radio commentator and television presenter. Moore's early interest in astro ...
suggested that this in fact refers to another star that lies visually between Mizar and Alcor. 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. Liebknecht thought it was a planet, but it had already been observed in exactly the same position by
Benedetto Castelli Benedetto Castelli (1578 – 9 April 1643), born Antonio Castelli, was an Italians, Italian mathematician. Benedetto was his name in religion on entering the Benedictine Order in 1595. Life Born in Brescia, Castelli studied at the University of ...
approximately a century earlier, which indicated it was a background star. Agnes M. Clerke wrote:


6-star system

Benedetto Castelli Benedetto Castelli (1578 – 9 April 1643), born Antonio Castelli, was an Italians, Italian mathematician. Benedetto was his name in religion on entering the Benedictine Order in 1595. Life Born in Brescia, Castelli studied at the University of ...
, 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.


See also

*
Star system A star system or stellar system is a small number of stars that orbit each other, bound by gravity, gravitational attraction. It may sometimes be used to refer to a single star. A large group of stars bound by gravitation is generally calle ...


References


External links


Mizar
an

articles at Jim Kaler's ''Stars'' website

{{Portal bar, Astronomy, Stars, Outer space Big Dipper Stars with proper names Ursa Major Binary stars