Merak (star)

Coordinates: Sky map 11h 01m 50.5s, +56° 22′ 57″
Source: Wikipedia, the free encyclopedia.
Merak
Location of Merak (circled)
Observation data
J2000.0
Constellation Ursa Major
Right ascension 11h 01m 50.47654s[1]
Declination +56° 22′ 56.7339″[1]
Apparent magnitude (V) +2.37[2]
Characteristics
Spectral type A1IVps[3]
U−B color index +0.00[2]
B−V color index -0.02[2]
Variable type Suspected
Distance
79.7 ± 0.3 ly
(24.45 ± 0.10 pc)
Absolute magnitude (MV)+0.61[5]
Details
Myr
HIP 53910, HR 4295, PPM 32912, SAO 27876[11]
Database references
SIMBADdata
Size comparison between the Sun, Beta Ursae Majoris, Pollux, and Arcturus.

Merak /ˈmɪəræk/, also called Beta Ursae Majoris (β Ursae Majoris, abbreviated Beta UMa, β UMa),[12][13] is a star in the northern constellation of Ursa Major.

The

Alpha Ursae Majoris (Dubhe) extends to Polaris
, the north star.

Spectral classification

In 1943, β Ursae Majoris was listed as a spectral standard for the class of A1 V.

luminosity classes for early A-class stars, β Ursae Majoris was assigned that class A0 IV.[15] This was later revised to A1 IV.[3] It is considered to be a mild Am star, a type of chemically peculiar star with unusually strong lines of certain metallic elements.[16]

Properties

Based upon

A-type stars.[17] It is larger than the Sun, with about 2.7 times the mass and 2.84 times the solar radius. If they were viewed from the same distance, Beta Ursae Majoris would appear much brighter than the Sun, as it is radiating 68 times the Sun's luminosity.[6][18]

Observation of the star in the infrared reveal an excess emission that suggests the presence of a circumstellar debris disk of orbiting dust,[6] much like those discovered around Fomalhaut and Vega. The mean temperature of this disk is 120 K,[18] indicating that it is centered at a radius of 47 AU from the host star.[6] The dust has an estimated mass of about 0.27% the mass of the Earth.[18]

Beta Ursae Majoris is one of five stars in the Big Dipper that form a part of a loose

Gamma Ursae Majoris at 11 light-years (3.4 pc); much closer to each other than these stars are to the Earth.[19]

Nomenclature

β Ursae Majoris (Latinised to Beta Ursae Majoris) is the star's Bayer designation.

It bore the traditional name Merak derived from the Arabic المراق al-marāqq 'the loins' (of the bear).[10] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[20] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included Merak for this star.[21]

The

Seven Rishis.[10]

In

Chinese name for Beta Ursae Majoris itself is 北斗二 (Běi Dǒu èr, English: the Second Star of Northern Dipper) and 天璇 (Tiān Xuán, English: Star of Celestial Rotating Jade).[22]

In culture

USS Merak (1918) and USS Merak (AF-21) are both United States navy ships.

See also

References

  1. ^
    S2CID 18759600
    .
  2. ^
    Bibcode:1966CoLPL...4...99J
  3. ^
    S2CID 119262858
    .
  4. Bibcode:1967IAUS...30...57E
    .
  5. doi:10.1086/300465
    .
  6. ^
    S2CID 18883195
  7. ^
    S2CID 18993744
    . See Table 10.
  8. ^
    doi:10.1051/0004-6361:20053222
  9. S2CID 18475298
  10. ^
    Bibcode:1899sntm.book.....A
  11. Centre de Données astronomiques de Strasbourg
    , retrieved 2012-01-01
  12. ISBN 978-1-931559-44-7
    .
  13. ^ "IAU Catalog of Star Names". Retrieved 28 Apr 2019.
  14. Bibcode:1943assw.book.....M
    .
  15. doi:10.1086/190209
    .
  16. doi:10.1051/0004-6361/200810788
    .
  17. Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original
    on 2012-03-18, retrieved 2012-01-16
  18. ^
    S2CID 11879505
  19. S2CID 119226823
  20. ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
  21. ^ "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
  22. ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 15 日
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