A report on Double star, Binary 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.
Binary system of two stars
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.
Edge-on disc of gas and dust present around the binary star system HD 106906
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.
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.
Radial velocity curves for the two almost identical components
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)

This occurs because the pair either forms a binary star (i.e. a binary system of stars in mutual orbit, gravitationally bound to each other) or is an optical double, a chance line-of-sight alignment of two stars at different distances from the observer.

- Double star

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

- Mizar

Mizar is a visual double with a separation of 14.4 arcseconds, each of which is a spectroscopic binary.

- Mizar

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

- Double star

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

- Binary star

Early examples include Mizar and Acrux.

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

2 related topics with Alpha

Overall
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.

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.

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.