Alcor (star)

Coordinates: Sky map 13h 25m 13.5s, +54° 59′ 17″
Source: Wikipedia, the free encyclopedia.
Alcor
Location of Alcor (
Mizar
is circled, Alcor is invisible beside it at this scale.)
Observation data
J2000.0
Constellation Ursa Major
Right ascension 13h 25m 13.53783s[1]
Declination +54° 59′ 16.6548″[1]
Apparent magnitude (V) +3.99[2]
Characteristics
Spectral type A5Vn[3] / M3-4[4]
Distance
81.7 ± 0.3 ly
(25.06 ± 0.08 pc)
Absolute magnitude (MV)+2.00[2]
Details
Myr
SAO 28751, WDS
 J13239+5456C
Database references
SIMBADdata

Alcor (

Mizar, the two stars forming a naked eye double in the handle of the Big Dipper (or Plough) asterism in Ursa Major. The two lie about 83 light-years away from the Sun, as measured by the Hipparcos astrometry
satellite.

Nomenclature

Alcor has the Flamsteed designation 80 Ursae Majoris. Alcor derives from Arabic الخوار al-khawāri, meaning 'faint one';[9][10] notable as a faintly perceptible companion of Mizar.[11]

In 2016, the

Working Group on Star Names (WGSN)[12] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[13] included a table of the first two batches of names approved by the WGSN; which included Alcor for 80 UMa.[14]

Mizar and Alcor

Main article: Mizar and Alcor
Mizar and Alcor in constellation Ursa Major.

With normal eyesight Alcor appears at about 12

spectral class
A5V.

Mizar's and Alcor's

Ursa Major Moving Group, a mostly dispersed group of stars sharing a common birth. However, it has yet to be demonstrated conclusively that they are gravitationally bound. Recent studies indicate that Alcor and Mizar are somewhat closer together than previously thought: approximately 74,000 ± 39,000 AU, or 0.5–1.5 light-years. The uncertainty is due to our uncertainty about the exact distances from us. If they are exactly the same distance from us (somewhat unlikely) then the distance between them is only 17,800 AU (0.281 light-years).[2]

Alcor B

The Big Dipper's bowl and part of the handle photographed from the International Space Station. Mizar and Alcor are at the upper right.

In 2009, Alcor was discovered to have a companion star Alcor B, a magnitude 8.8 red dwarf.[15]

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.[4]

Alcor B is one

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-closest stellar sextuplet—only

Ursa Major Moving Group, a stellar group of stars of similar ages and velocities,[2]
and the closest cluster-like object to Earth.

Other names

In Arabic, Alcor is also known as Al-Sahja (the rhythmical form of the usual al-Suhā) meaning "forgotten", "lost", or "neglected".[17]

In traditional

Saptarishi
.

In the

Miꞌkmaq myth of the great bear and the seven hunters,[19]
Mizar is Chickadee and Alcor is his cooking pot.

Military namesakes

USS Alcor (AD-34) and USS Alcor (AK-259) are both United States Navy ships.

References

  1. ^
    S2CID 18759600
    .
  2. ^
    S2CID 51834159
    .
  3. doi:10.1086/191349
    .
  4. ^
    S2CID 6052794
    .
  5. doi:10.1086/374996
    .
  6. S2CID 16600591
    .
  7. S2CID 33401607
    .
  8. ISBN 978-1-931559-44-7
    .
  9. ^ "Britannica - Alcor". 2009-12-21. Retrieved 2022-12-29.
  10. Arabic star names
    , published in Popular Astronomy, January 1895, by Professor Robert H. West, of the Syrian Protestant College at Beirut.
  11. PMID 18929764
    .
  12. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  13. ^ "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
  14. ^ "IAU Catalog of Star Names". Retrieved 28 July 2016.
  15. ^ "New Star Found in Big Dipper". Space.com. 10 December 2009. Retrieved 2019-10-30.
  16. ^ Dan Vergano (December 11, 2009). "Two Big Dipper constellation stars actually six". USA Today. Retrieved 2019-10-30.
  17. ^ "Star Tales – Mizar and Alcor". Retrieved 2024-07-22.
  18. ISBN 978-81-223-0366-7
    . ... the seven rishis in the constellation Saptarishi (Ursa Major) ... In Vasishta (Zeta), its tiny companion star is named after Arundhati, the wife of Vasishta ... today known by their Arabic names Dubhe (Kratu), Merak (Pulaha), Phekda (Pulastya), Megrez (Atri), Benetnash (Marichi) and Mizar (Vasishta) ...
  19. ^ "The Celestial Bear, A Micmac Legend". 2009-02-11. Archived from the original on 2017-10-18. Retrieved 2018-01-01.
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