page_title: Alcor (star)
section_title: Alcor B
hierarchical_section_title: Alcor (star) / Alcor B
caption_attribution_description: English: The bowl and a portion of the ?handle? stars of the en:Big Dipper are visible in this photograph taken by astronaut Donald R. Pettit, en:Expedition 6 NASA ISS science officer, on board the en:International Space Station (ISS).
context_page_description: Alcor is a binary star system in the constellation of Ursa Major. It is the fainter companion of Mizar, the two stars forming a naked eye double in the handle of the Big Dipper asterism in the constellation of Ursa Major. The two both lie about 83 light-years away from the Sun, as measured by the Hipparcos astrometry satellite.
context_section_description: In 2009, Alcor was discovered to have a companion star Alcor B, a magnitude 8.8 red dwarf.
  Alcor B was discovered independently by two groups.  One group led by Eric Mamajek (University of Rochester) and colleagues at Steward Observatory University of Arizona used adaptive optics on the 6.5-meter telescope at MMT Observatory.  Another led by Neil Zimmerman, a graduate student at Columbia University and member of Project 1640, an international collaborative team that includes astrophysicists at the American Museum of Natural History, the University of Cambridge's Institute of Astronomy, the California Institute of Technology, and NASA's Jet Propulsion Laboratory, used the 5-meter Hale telescope at Palomar Observatory.  The companion star was unofficially nicknamed "Eleonora" by the former group.
  Alcor B is one second of arc away from Alcor A.  Its spectral type is M3-4 and it is a main sequence star, a red dwarf.
  Alcor A and B are situated 1.2 light years away from, and are co-moving with, the Mizar quadruple system, making the system the second known stellar sextuplet—only Castor (star) is closer. The Mizar-Alcor stellar sextuple system belongs to the Ursa Major Moving Group, a nearby stellar group of stars of similar ages and velocities.
caption: The Big Dipper's bowl and part of the handle photographed from the International Space Station. Mizar and Alcor are at the upper right.
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