A report on Double star and Mizar

Astronomers have mistakenly reported observations of a double star in place of J 900 and a faint star in the constellation of Gemini.
The Big Dipper's bowl and part of the handle photographed from the International Space Station. Mizar and Alcor are at the upper right.
Artist's impression of the discs around the young stars HK Tauri A and B.
The multiple star system of Mizar (the double star on the right) and Alcor (left). The unrelated, fainter star Sidus Ludovicianum can be seen lower down.
Radial velocity curves for the two almost identical components

It forms a well-known naked eye double star with the fainter star Alcor, and is itself a quadruple star system.

- Mizar

Mizar, in Ursa Major, was observed to be double by Benedetto Castelli and Galileo.

- Double star
Astronomers have mistakenly reported observations of a double star in place of J 900 and a faint star in the constellation of Gemini.

4 related topics with Alpha

Overall

Binary system of two stars

Binary star

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System of two stars that are gravitationally bound to and in orbit around each other.

System of two stars that are gravitationally bound to and in orbit around each other.

Binary system of two stars
Edge-on disc of gas and dust present around the binary star system HD 106906
Algol B orbits Algol A. This animation was assembled from 55 images of the CHARA interferometer in the near-infrared H-band, sorted according to orbital phase.
Artist's conception of a cataclysmic variable system
Artist's impression of the binary star system AR Scorpii
Artist rendering of plasma ejections from V Hydrae
Artist's impression of the sight from a (hypothetical) moon of planet HD 188753 Ab (upper left), which orbits a triple star system. The brightest companion is just below the horizon.
Schematic of a binary star system with one planet on an S-type orbit and one on a P-type orbit
The two visibly distinguishable components of Albireo
Luhman 16, the third closest star system, contains two brown dwarfs.
Planet Lost in the Glare of Binary Stars (illustration)

The more general term double star is used for pairs of stars which are seen to be close together in the sky.

Early examples include Mizar and Acrux.

Mizar and Alcor in constellation Ursa Major

Mizar and Alcor

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Mizar and Alcor in constellation Ursa Major

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.

Mizar is the second star from the end of the Big Dipper's handle, and Alcor its fainter companion.

Star system named DI Cha. While only two stars are apparent, it is actually a quadruple system containing two sets of binary stars.

Star system

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Small number of stars that orbit each other, bound by gravitational attraction.

Small number of stars that orbit each other, bound by gravitational attraction.

Star system named DI Cha. While only two stars are apparent, it is actually a quadruple system containing two sets of binary stars.
Orbits of the HR 6819 hierarchical triple star system: an inner binary with one star (orbit in blue) and a black hole (orbit in red), encircled by another star in a wider orbit (also in blue).
Subsystem notation in Tokovinin's Multiple Star Catalogue
Sirius A (center), with its white dwarf companion, Sirius B (lower left) taken by the Hubble Space Telescope.
HD 98800 is a quadruple star system located in the TW Hydrae association.

A star system of two stars is known as a binary star, binary star system or physical double star.

Mizar is often said to have been the first binary star discovered when it was observed in 1650 by Giovanni Battista Riccioli, p. 1 but it was probably observed earlier, by Benedetto Castelli and Galileo. Later, spectroscopy of its components Mizar A and B revealed that they are both binary stars themselves.

The constellation Ursa Major as it can be seen by the unaided eye.

Ursa Major

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Constellation in the northern sky, whose associated mythology likely dates back into prehistory.

Constellation in the northern sky, whose associated mythology likely dates back into prehistory.

The constellation Ursa Major as it can be seen by the unaided eye.
Ursa Major and Ursa Minor in relation to Polaris
Ursa Major shown on a carved stone, c.1700, Crail, Fife
H. A. Rey's alternative asterism for Ursa Major can be said to give it the longer head and neck of a polar bear, as seen in this photo, from the left side.
Ursa Major as depicted in Urania's Mirror, a set of constellation cards published in London c.1825.
Johannes Hevelius drew Ursa Major as if being viewed from outside the celestial sphere.
Starry Night Over the Rhone by Vincent van Gogh (1888)
Polaris and the Big Dipper on the flag of Alaska.
The Pinwheel Galaxy

ζ Ursae Majoris, Mizar, the second star in from the end of the handle of the Big Dipper, and the constellation's fourth-brightest star. Mizar, which means "girdle," forms a famous double star, with its optical companion Alcor (80 Ursae Majoris), the two of which were termed the "horse and rider" by the Arabs.