Phecda

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"Phad" redirects here. For scroll painting style, see Phad painting.
Phecda
Location of Phecda (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Major
Right ascension 11h 53m 49.84732s[1]
Declination +53° 41′ 41.1350″[1]
Apparent magnitude (V) 2.438[2]
Characteristics
Spectral type A0 Ve + K2 V[3]
U−B color index +0.008[2]
B−V color index –0.013[2]
Distance
83.2 ± 0.8 ly
(25.5 ± 0.3 pc)
Absolute magnitude (MV)0.4[5]
Argument of periastron
(ω)
(secondary)		185 ± 37°
Details
γ UMa A
Gyr
γ UMa B
Mass0.79[3] M☉
Luminosity0.397[3] L☉
Temperature4,780[3] K
HIP 58001, HR 4554, PPM 33292, SAO 28179.[11]
Database references
SIMBADdata

Phecda

spectrum of this star has served as one of the stable anchor points by which other stars are classified.[14] Based upon parallax measurements with the Hipparcos astrometry satellite,[15][16] it is located at distance of around 83.2 light-years (25.5 parsecs) from the Sun.[1]

It is more familiar to most observers in the

Delta Ursae Majoris (Megrez, upper-left). Along with four other stars in this well-known asterism, Phecda forms a loose association of stars known as the Ursa Major moving group.[7] Like the other stars in the group, it is a main sequence
star, as the Sun is, although somewhat hotter, brighter and larger.

Phecda is located in relatively close physical proximity to the prominent

Beta Ursae Majoris is separated from Gamma Ursae Majoris by 11.0 ly (3.4 pc).[17]

Nomenclature

γ Ursae Majoris (Latinised to Gamma Ursae Majoris) is the star's Bayer designation.

It bore the traditional names Phecda or Phad, derived from the

Working Group on Star Names (WGSN)[19] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[20]
included a table of the first two batches of names approved by the WGSN, which included Phecda for this star.

To the

seven rishis.[10]

In

Chinese name for Gamma Ursae Majoris itself is 北斗三 (Běi Dǒu sān, English: the Third Star of Northern Dipper) and 天璣 (Tiān Jī, English: Star of Celestial Shining Pearl).[21]

Properties

Gamma Ursae Majoris is an

mas.[23] It has an estimated age of 300 million years.[9]

Gamma Ursae Majoris is also an

barycenter. From this, an orbital period of 20.5 years has been calculated.[5] The secondary star is a K-type main-sequence star that is 0.79 times as massive as the Sun, and with a surface temperature of 4,780 K.[3]

References

  1. ^
    S2CID 18759600
  2. ^
    Bibcode:1986A&AS...65..405O
  3. ^
    S2CID 73534476
    .
  4. Bibcode:1999VeARI..35....1W
  5. ^
    S2CID 119252073
    .
  6. ^
    S2CID 119512018
  7. ^
    doi:10.1086/368241
  8. ^
    S2CID 18475298
  9. ^
    S2CID 14116473
  10. ^
    Bibcode:1899sntm.book.....A
  11. Centre de Données astronomiques de Strasbourg
    , retrieved 2011-12-29
  12. ISBN 978-1-931559-44-7
    .
  13. ^ "IAU Catalog of Star Names". Retrieved 28 July 2016.
  14. Bibcode:1993AAS...183.1710G, archived from the original
    on 2019-06-25, retrieved 2012-02-04
  15. Bibcode:1997A&A...323L..49P
  16. ISBN 978-3-642-11601-8
  17. ^
    S2CID 119226823
  18. ISBN 0-521-59889-3
  19. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  20. ^ "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
  21. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 15 日
  22. doi:10.1051/aas:1998101
  23. doi:10.1086/301114
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