Delta Geminorum
Template:Location mark Location of δ Geminorum (circled) | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Gemini |
| Right ascension | Template:RA[1] |
| Declination | Template:DEC[1] |
| Apparent magnitude (V) | +3.53[2] |
| Characteristics | |
| Spectral type | F0 IV[3] |
| U−B Template:Engvar | +0.04[2] |
| B−V Template:Engvar | +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 mas[1] |
| Distance | Template:Rnd ± Template:Rnd ly (Template:Rnd ± Template:Rnd pc) |
| Absolute magnitude (MV) | 1.95[5] |
| Orbit[6] | |
| Primary | Aa |
| Companion | Ab |
| Period (P) | 2,238.7 days |
| Eccentricity (e) | 0.3530 |
| Orbit[7] | |
| Primary | A |
| Companion | B |
| Period (P) | ~550 yr |
| Semi-major axis (a) | Script error: No such module "val".″ |
| Eccentricity (e) | Script error: No such module "val". |
| Inclination (i) | Script error: No such module "val".° |
| Longitude of the node (Ω) | Script error: No such module "val".° |
| Periastron epoch (T) | Script error: No such module "val". |
| Argument of periastron (ω) (secondary) | Script error: No such module "val".° |
| Details | |
| Mass | 1.57[8] Template:Solar mass |
| Radius | 2.31[9] Template:Solar radius |
| Luminosity | 9.88[9] Template:Solar luminosity |
| Temperature | 6,900[10] K |
| Metallicity [Fe/H] | –0.26[10] dex |
| Rotational velocity (v sin i) | 129.7[11] km/s |
| Age | 1.6[10] Gyr |
| Metallicity [Fe/H] | {{{metal_fe2}}} dex |
| Other designations | |
| Wasat, 55 Geminorum, BD+22°1645, FK5 279, Gl 271, HD 56986, HIP 35550, HR 2777, SAO 79294.[3] | |
| Database references | |
| SIMBAD | data |
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Delta Geminorum (δ Geminorum, abbreviated Delta Gem, δ Gem), formally named Wasat Template:IPAc-en,[12][13] 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".[14][15] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[16] 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.[13]
In Chinese, Script error: No such module "Lang". (Script error: No such module "Lang".), meaning Celestial Wine Cup, refers to an asterism consisting of Delta Geminorum, 57 Geminorum and Omega Geminorum.[17] Consequently, Delta Geminorum itself is known as Script error: No such module "Lang". (Script error: No such module "Lang"., Template:Langx.).[18] From this Chinese name, the name Ta Tsun has appeared.[19]
Properties
Delta Geminorum is a subgiant star with the stellar classification F0 IV.[3] It is about Script error: No such module "convert". distant.[1] This star has 1.57 times the mass of the Sun[8] and is rotating rapidly with a projected rotational velocity of 129.7 km s−1.[11] The estimated age is 1.6 billion years.[10]
It has an apparent visual magnitude of +3.53,[2] allowing it to be 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.[21] 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.Script error: No such module "Unsubst". In 1930, the dwarf planet Pluto was discovered about 0.5° to the east of this star by American astronomer Clyde Tombaugh.[22]
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.[6] 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 in the order of a hundred years, with a high but uncertain eccentricity of Script error: No such module "val"..[7] Although according to Evans et al. (1966) its radial velocity is away from the Sun,[4] it is actually approaching the Solar System. In about 1.1 million years, it will make its closest approach at a separation of roughly Script error: No such module "convert"..[23]
References
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- ↑ a b c d Script error: No such module "citation/CS1".
- ↑ a b Script error: No such module "citation/CS1".Script error: No such module "Unsubst".
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- ↑ a b Script error: No such module "citation/CS1".
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- ↑ Template:In lang 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, Template:ISBN.
- ↑ Template:In lang 香港太空館 - 研究資源 - 亮星中英對照表 Script error: No such module "webarchive"., Hong Kong Space Museum. Accessed on line November 23, 2010.
- ↑ Richard Hinckley Allen: Star Names — Their Lore and Meaning: Gemini
- ↑ Script error: No such module "citation/CS1".
- ↑ In the Sky Earth astronomy reference utility showing the ecliptic and relevant date as at J2000 - present
- ↑ Script error: No such module "citation/CS1".
- ↑ Script error: No such module "citation/CS1".
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