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| Mizar and Alcor | |
|---|---|
| Name | Mizar and Alcor |
| Constellation | Ursa Major |
| Epoch | J2000 |
| Component1 | Mizar |
| Component2 | Alcor |
| Type | Multiple star system |
| Distance | ~83 light-years |
Mizar and Alcor Mizar and Alcor form a naked-eye double in the constellation Ursa Major near the Big Dipper asterism and have been used as a test of eyesight since antiquity. The pair occupy a prominent position in Northern Hemisphere sky lore associated with Polaris, Sirius, Betelgeuse, Vega and serve as reference points in observational programs by institutions such as the Royal Astronomical Society, Smithsonian Institution, European Southern Observatory, National Aeronautics and Space Administration, and Space Telescope Science Institute.
Mizar (ζ1 Ursae Majoris) and Alcor (80 Ursae Majoris) are situated in the tail of Ursa Major within the Big Dipper and are separated by about 11.8 arcminutes as seen from Earth. Mizar is a visually brighter component with known spectroscopic companions identified by techniques used at facilities like Palomar Observatory, Keck Observatory, Very Large Telescope, and Arecibo Observatory, while Alcor is a fainter star with its own low-mass companion detected by instruments developed at Caltech, MIT, Harvard-Smithsonian Center for Astrophysics, and Max Planck Society institutes. The system's proximity to Sun and position within the local volume has made it a target for missions including Hipparcos, Gaia, Hubble Space Telescope, and ground-based interferometers from CHARA Array and VLTI.
Mizar exhibits multiple hierarchical components: historical observations resolved Mizar A and Mizar B as an optical pair noted by observers from Ptolemy through Tycho Brahe to Johannes Hevelius, while modern spectroscopy and interferometry revealed spectroscopic binaries and higher-order multiplicity studied with equipment from CERN-affiliated projects and national observatories in France, Germany, Japan, United Kingdom, and United States. Alcor hosts a low-mass companion characterized through near-infrared imaging using detectors developed by NASA, JAXA, and research groups at University of California, University of Cambridge, and Institute for Advanced Study. Parallax and proper motion measurements by Hipparcos and Gaia indicate similar distances and kinematics to members of moving groups traced to associations like the Ursa Major Moving Group and compared with stellar populations studied in surveys by Sloan Digital Sky Survey, 2MASS, WISE and Pan-STARRS. Spectral classifications link Mizar to A-type main-sequence characteristics akin to stars cataloged in the Henry Draper Catalogue and Alcor to late A- or early F-type designations, with rotational velocities, metallicities and ages constrained via models by researchers affiliated with Harvard University, Princeton University, University of Chicago, and Caltech.
References to the Mizar–Alcor pairing appear in works by Ptolemy and medieval Arabian astronomers; they are prominent in folklore from cultures including Ancient Greece, Navajo Nation, Sami people, Hinduism, Japanese mythology and European traditions recorded by chroniclers associated with institutions like Bodleian Library, Vatican Library, British Museum and scholars such as Claudius Ptolemy, Al-Sufi, Tycho Brahe, and Johannes Hevelius. The pair served as vision tests for sailors in archives of Royal Navy practices and appear in navigation manuals used by explorers like Christopher Columbus and James Cook whose logs are preserved in repositories such as the National Maritime Museum and Society for Nautical Research. Literary references span authors from Homer and Dante Alighieri through William Shakespeare to modern poets curated by the Library of Congress and anthologies edited by Oxford University Press.
Telescopic splitting of the Mizar visual pair dates to early use of refractors and reflectors by astronomers including Galileo Galilei and observers at Royal Observatory, Greenwich; later spectroscopic characterization used instruments pioneered by Joseph Fraunhofer and laboratories at Royal Observatory Edinburgh and Lick Observatory. Adaptive optics systems from Caltech and National Optical Astronomy Observatory enabled high-resolution imaging, while long-baseline optical interferometry from CHARA Array and radio interferometry techniques inspired by Karl Jansky and developed at NRAO provided precision astrometry. Photon-counting detectors and digital sensors produced by groups at Bell Labs, Bell Laboratories successors, MIT Lincoln Laboratory and industry partners enabled radial velocity studies comparable to those used in exoplanet searches by teams at European Southern Observatory and Keck Observatory.
Contemporary studies of Mizar and Alcor address stellar multiplicity, dynamical stability, angular momentum evolution, and stellar evolution benchmarks used to calibrate isochrones in models from Geneva Observatory and computational frameworks at Max Planck Institute for Astronomy, Carnegie Institution for Science, Princeton Plasma Physics Laboratory and university groups at University of California, Berkeley and University of Toronto. The system informs research on hierarchical systems relevant to surveys by Gaia, time-domain programs like Zwicky Transient Facility and spectroscopic campaigns conducted by Sloan Digital Sky Survey. Studies contribute to calibration of distance scales alongside datasets from Hubble Space Telescope Key Projects, comparison with clusters such as Hyades and Pleiades, and stellar rotation work linked to projects at European Space Agency, NASA and national laboratories.
Mizar and Alcor feature in popular astronomy guides published by National Geographic Society, Time and Scientific American, and appear in planetarium programs at institutions like Hayden Planetarium and Griffith Observatory. The pair are mentioned in fiction by authors represented in collections from Penguin Books, HarperCollins and Vintage Books, and are used as practical reference points in amateur observing guides from Royal Astronomical Society of Canada, Astronomical League and observatory outreach by Sierra Club affiliates. Mariners and aviators trained at facilities such as United States Naval Academy and Royal Air Force College Cranwell have historically used the pair, alongside navigational stars like Polaris and Sirius, in celestial navigation curricula archived by United States Naval Observatory.
Category:Binary stars Category:Ursa Major