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Mizar (star)

 

 
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Mizar (star)
 
 
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Mizar (? UMa / ? Ursae Majoris) is a star
Star

A star is a massive, luminous ball of Plasma that is held together by its own gravity. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth....
 in the constellation
Constellation

A constellation is a group of stars that appear to have a physical proximity in the sky. The stars in a constellation are often vastly distant from each other, but they appear close to each other from the perspective of Earth....
 Ursa Major
Ursa Major

Ursa Major is a constellation visible throughout the year in most of the northern hemisphere. Its name means the Great Bear in Latin. It is dominated by the widely recognized asterism known as the Big Dipper or Plough, which is a useful pointer toward north, and which has mythological significance in numerous world cultures....
 and is the second star from the end of the Big Dipper
Big Dipper

The seven brightest stars of the constellation Ursa Major, the Great Bear, form a well-known asterism that has been recognized as a distinct grouping in many cultures from time immemorial....
's handle. Its apparent magnitude is 2.23 and its spectral class is A1V. Mizar's name comes from the Arabic
Arabic language

Arabic is a Central Semitic language, thus related to and classified alongside other Semitic languages languages such as Hebrew language and Aramaic language....
 ???? mi'zar, meaning a waistband or girdle. In Chinese it is ??(???).

With normal eyesight one can make out a faint companion just to the east, named Alcor or 80 Ursae Majoris.






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Mizar (? UMa / ? Ursae Majoris) is a star
Star

A star is a massive, luminous ball of Plasma that is held together by its own gravity. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth....
 in the constellation
Constellation

A constellation is a group of stars that appear to have a physical proximity in the sky. The stars in a constellation are often vastly distant from each other, but they appear close to each other from the perspective of Earth....
 Ursa Major
Ursa Major

Ursa Major is a constellation visible throughout the year in most of the northern hemisphere. Its name means the Great Bear in Latin. It is dominated by the widely recognized asterism known as the Big Dipper or Plough, which is a useful pointer toward north, and which has mythological significance in numerous world cultures....
 and is the second star from the end of the Big Dipper
Big Dipper

The seven brightest stars of the constellation Ursa Major, the Great Bear, form a well-known asterism that has been recognized as a distinct grouping in many cultures from time immemorial....
's handle. Its apparent magnitude is 2.23 and its spectral class is A1V. Mizar's name comes from the Arabic
Arabic language

Arabic is a Central Semitic language, thus related to and classified alongside other Semitic languages languages such as Hebrew language and Aramaic language....
 ???? mi'zar, meaning a waistband or girdle. In Chinese it is ??(???).

With normal eyesight one can make out a faint companion just to the east, named Alcor or 80 Ursae Majoris. Alcor is of magnitude 3.99 and spectral class A5 V. Mizar and Alcor together are sometimes called the "Horse and Rider
Horse and Rider

The Horse and Rider is an informal name given to the asterism composed of the two stars Mizar and Alcor because of their close proximity in the sky....
," 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 motion
Proper motion

The proper motion of a star is its angular change in position over time as seen from the Sun, as inferred after improper motions are accounted for....
s show they move together (they are both members of the Ursa Major Moving Group
Ursa Major Moving Group

The Ursa Major Moving Group, also known as Collinder 285, is the closest moving group to Earth, that is, a set of stars with common velocities in space, thought to have a common origin....
), it is not believed they form a true binary star
Binary star

A binary star is a star system consisting of two stars orbiting around their common center of mass. The brighter star is called the primary and the other is its companion star or secondary....
 system, but simply an optical binary.

More components of the Mizar system were discovered with the advent of the telescope and spectroscopy; a fine, easily-split visual target, Mizar was the first telescopic binary discovered—most probably by Benedetto Castelli
Benedetto Castelli

Benedetto Castelli, born Antonio Castelli was an Italy mathematician. He took the name "Benedetto" upon entering the Benedictine Order in 1595....
 who in 1617 asked Galileo Galilei
Galileo Galilei

Galileo Galilei was a Grand Duchy of Tuscany physicist, mathematician, astronomer, and philosopher who played a major role in the Scientific Revolution....
 to observe it. Galileo then produced a detailed record of the double star. Later, around 1650, Riccioli
Giovanni Battista Riccioli

Giovanni Battista Riccioli , was an Italy astronomer. He was a Jesuit who entered the order in 1614. He was also the first person to measure the rate of acceleration of a freely falling body....
 wrote of Mizar appearing as a double. The secondary star, Mizar B, has magnitude 4.0 and spectral class A7, and comes within 380 AU
Astronomical unit

An astronomical unit is a unit of length based on the mean distance from the Earth to the Sun. The precise value of the AU is currently accepted as 149,597,870,691 Plus-minus sign 6 metres ....
 of the primary; the two take thousands of years to revolve around each other. Mizar A was the first spectroscopic binary to be discovered, by Pickering
Edward Charles Pickering

Edward Charles Pickering was an United States astronomer and physicist, brother of William Henry Pickering.Along with Hermann Carl Vogel, Pickering discovered the first spectroscopic binary stars....
 in 1889. The two components are both about 35 times as bright as the sun, and revolve around each other in about 20 days. Mizar B was later found to be a spectroscopic binary as well. In 1996 the components of the Mizar A binary system were imaged in extremely high resolution using the Navy Prototype Optical Interferometer
Navy Prototype Optical Interferometer

The Navy Prototype Optical Interferometer is an interferometer operated by the US Naval Observatory, the Naval Research Laboratory and The Lowell Observatory....
.

The whole four-star system lies about 78 light-years away from us. The components are all members of the Ursa Major moving group
Ursa Major Moving Group

The Ursa Major Moving Group, also known as Collinder 285, is the closest moving group to Earth, that is, a set of stars with common velocities in space, thought to have a common origin....
, a mostly dispersed group of stars sharing a common birth, as determined by proper motion. The other stars of the Big Dipper, except Dubhe
Alpha Ursae Majoris

Alpha Ursae Majoris is the second-brightest star in the constellation of Ursa Major . It also has the traditional name Dubhe.It forms part of the Big Dipper , and is the northern of the pointers, the two stars of Ursa Major which point towards Polaris, the North Star....
 and Alkaid
Eta Ursae Majoris

Eta Ursae Majoris is a star in the constellation Ursa Major. It also has the traditional names Alkaid and Benetnash .It is known as ??? or ?? in Chinese....
, belong to this group as well.

Other Names

Mizar is known as Vasistha
Vasistha

Vasistha , in Hindu mythology was one of the Saptarishis in the seventh, i.e the present Manvantara, and the Rajpurohit / Rajguru of the Suryavamsha or Solar Dynasty....
 and Alcor is known as Arundhati
Arundhati

Arundhati can refer to:* Arundhati , a 2009 Telugu movie directed by Kodi Ramakrishna* Arundhati , the Hindu goddess of the sky, stars and night time....
 in Indian astrological books.

See also

  • Mizar in fiction


External links

  • and articles in Jim Kaler's Stars website
  • (using aperture synthesis
    Aperture synthesis

    Aperture synthesis or synthesis imaging is a type of interferometry that mixes signals from a collection of telescopes to produce images having the same angular resolution as an instrument the size of the entire collection....
    )
  • (a comprehensive article about the system)
Dipper