Delta Geminorum

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Delta Geminorum
Diagram showing star positions and boundaries of the Gemini constellation and its surroundings
Cercle rouge 100%.svg

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]
Astrometry
Radial velocity (Rv) +4.1[4] km/s
Proper motion (μ) RA: –15.13[1] mas/yr
Dec.: –9.79[1] mas/yr
Parallax (π) 53.94 ± 0.66[1] mas
Distance 60.5 ± 0.7 ly
(18.5 ± 0.2 pc)
Details
Mass 1.57[5] M☉
Temperature 6,900[6] K
Metallicity [Fe/H] –0.26[6] dex
Rotational velocity (v sin i) 129.7[7] km/s
Age 1.6[6] Gyr
Other designations
Wasat, 55 Geminorum, BD+22 1645, FK5 279, GJ 271, HD 56986, HIP 35550, HR 2777, SAO 79294.[3]
Database references
SIMBAD data

Delta Geminorum (δ Gem, δ Geminorum) is a star in the constellation Gemini. It has the traditional name Wasat, which comes from the Arabic word for "middle".[8][9]

It has an apparent visual magnitude of +3.53,[2] allowing it to be seen with the naked eye. Wasat is only two-tenths of a degree south of the ecliptic, and therefore is occasionally occulted by the Moon and, more rarely, by a planet. 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.[10]

Wasat is the bright star next to Jupiter.[11] Jupiter is ~280x brighter.

In Chinese, 天樽 (Tiān Zūn), meaning Celestial Wine Cup, refers to an asterism consisting of δ Geminorum, 57 Geminorum and ω Geminorum.[12] Consequently, δ Geminorum itself is known as 天樽二 (Tiān Zūn èr, English: the Second Star of Celestial Wine Cup.).[13] From this Chinese name, the name Ta Tsun has appeared.[14]

Properties

Delta Geminorum is a subgiant star with the stellar classification F0 IV.[3] It is about 60.5 light-years (18.5 parsecs) distant.[1] This star has 1.57 times the mass of the Sun[5] and is rotating rapidly with a projected rotational velocity of 129.7 km s−1.[7] The estimated age is 1.6 billion years.[6]

Wasat is a member of 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.[15][16] 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).[17]

References

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External links

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Lua error in package.lua at line 80: module 'strict' not found.
  2. ↑ 2.0 2.1 2.2 2.3 Lua error in package.lua at line 80: module 'strict' not found.
  3. ↑ 3.0 3.1 3.2 Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ 4.0 4.1 Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ 5.0 5.1 Lua error in package.lua at line 80: module 'strict' not found.
  6. ↑ 6.0 6.1 6.2 6.3 Lua error in package.lua at line 80: module 'strict' not found.
  7. ↑ 7.0 7.1 Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  10. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  12. ↑ (Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
  13. ↑ (Chinese) 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.
  14. ↑ Richard Hinckley Allen: Star Names — Their Lore and Meaning: Gemini
  15. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  16. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  17. ↑ Lua error in package.lua at line 80: module 'strict' not found.
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