Delta Geminorum

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Delta Geminorum
Location of δ Geminorum (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Gemini
Right ascension 07h 20m 07.37978s[1]
Declination +21° 58′ 56.3377″[1]
Apparent magnitude (V) +3.53[2]
Characteristics
Spectral type F0 IV[3]
U−B color index +0.04[2]
B−V color index +0.34[2]
Distance
60.5 ± 0.7 ly
(18.5 ± 0.2 pc)
Absolute magnitude (MV)1.95[5]
Details
Gyr
HR 2777, SAO 79294.[3]
Database references
SIMBADdata

Delta Geminorum (δ Geminorum, abbreviated Delta Gem, δ Gem), formally named Wasat /ˈweɪsət/,[9][10] is a triple star system in the constellation of Gemini.

Nomenclature

δ Geminorum (Latinised to Delta Geminorum) is the system's Bayer designation.

It bore the traditional name Wasat, which derives from the Arabic word for "middle".[11][12] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[13] to catalogue and standardize proper names for stars. The WGSN approved the name Wasat for this star on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.[10]

In Chinese, 天樽 (Tiān Zūn), meaning Celestial Wine Cup, refers to an asterism consisting of Delta Geminorum, 57 Geminorum and Omega Geminorum.[14] Consequently, Delta Geminorum itself is known as 天樽二 (Tiān Zūn èr, English: the Second Star of Celestial Wine Cup.).[15] From this Chinese name, the name Ta Tsun has appeared.[16]

Properties

Wasat is the bright star next to Jupiter.[17] Jupiter is ~280× brighter.

Delta Geminorum is a

projected rotational velocity of 129.7 km s−1.[8] The estimated age is 1.6 billion years.[7]

It has an

seen with the naked eye. It is 0.18 degree south of the ecliptic so it is occasionally occulted by the Sun, Moon and, rarely, by a planet; and is eclipsed by the sun from about 10-12 July.[18] Thus the star can be viewed the whole night, crossing the sky, in mid-January. The last occultation by a planet was by Saturn on June 30, 1857, and the next will be by Venus on August 12, 2420.[citation needed] In 1930, the dwarf planet Pluto was discovered about 0.5° to the east of this star by American astronomer Clyde Tombaugh.[19]

Delta Geminorum is a triple star system. The inner components form a

spectroscopic binary with a period of 6.1 years (2,238.7 days) and an orbital eccentricity of 0.3530. A cooler class K companion is not apparent to the naked eye but clearly visible in a small telescope. It orbits the inner pair with a period of 1,200 years and an eccentricity of 0.11.[20][21] Although according to [4] its radial velocity is away from the Sun, it is actually approaching the Solar System. In about 1.1 million years, it will make its closest approach at a separation of roughly 6.7 ly (2.1 pc).[22]

References

  1. ^
    S2CID 18759600
  2. ^
    Bibcode:1966CoLPL...4...99J
  3. ^
    Centre de Données astronomiques de Strasbourg
    , retrieved 2011-06-03
  4. ^
    Bibcode:1967IAUS...30...57E. {{cite book}}: |journal= ignored (help
    )
  5. S2CID 8642707
  6. ^
    S2CID 119226823
  7. ^
    S2CID 11027621
  8. ^
    doi:10.1051/0004-6361:200810377[permanent dead link
    ]
  9. ISBN 978-1-931559-44-7
  10. ^ a b IAU Catalog of Star Names, retrieved 28 July 2016
  11. ^ Kaler, Jim (n.d.), "WASAT (Delta Geminorum)", Stars (University of Illinois sponsored website), retrieved July 29, 2014, The name is a mess, "Wasat" meaning "middle" in Arabic, but the middle of WHAT is not clear, whether the middle of Gemini, of the sky, or of the neighboring constellation Orion (which the Arabs referred to as the "Central One"), the star name improperly applied to our Delta.
  12. ^ Allen, Richard (1889). "The history of the star: Wasat, from p.234 of Star Names, Richard Hinckley Allen, 1889". Constellations of Words website. Retrieved July 29, 2014. Wasat and Wesat are from Al Wasat, the Middle, i.e. of the constellation; but some have referred this to the position of the star very near to the ecliptic, the central circle.
  13. ^ IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016
  14. ISBN 978-986-7332-25-7
    .
  15. ^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived August 19, 2010, at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
  16. ^ Richard Hinckley Allen: Star Names — Their Lore and Meaning: Gemini
  17. ^ King, Bob (12 December 2013), "To Delta Geminorum by way of Jupiter and Pluto", Astro Bob, Areavoices.com, retrieved 13 December 2013
  18. ^ In the Sky Earth astronomy reference utility showing the ecliptic and relevant date as at J2000 - present
  19. ISBN 0-521-82796-5
  20. doi:10.1086/431207
  21. University of Illinois
    , retrieved 2012-01-30
  22. doi:10.1051/0004-6361:20011330

External links
Retrieved from "https://en.wikipedia.org/w/index.php?title=Delta_Geminorum&oldid=1176940581"