Epoch J2000.0 Equinox J2000.0
|Right ascension||18h 20m 59.64354s|
|Declination||−29° 49′ 41.1659″|
|Apparent magnitude (V)||+2.70|
|Spectral type||K3 III|
|U−B color index||+1.55|
|B−V color index||+1.38|
|Radial velocity (Rv)||–19.9 km/s|
|Proper motion (μ)||RA: +32.54 mas/yr
Dec.: −25.57 mas/yr
|Parallax (π)||9.38 ± 0.18 mas|
|Distance||348 ± 7 ly
(107 ± 2 pc)
|Absolute magnitude (MV)||−1.99|
|δ Sgr A|
|Surface gravity (log g)||0.30 cgs|
|Metallicity [Fe/H]||−0.32 dex|
Delta Sagittarii (δ Sagittarii, abbreviated Delta Sgr, δ Sgr), also named Kaus Media, is a double star in the southern zodiac constellation of Sagittarius. The apparent visual magnitude of this star is +2.70, making it easily visible to the naked eye. Parallax measurements place the distance at roughly 348 light-years (107 parsecs) from the Sun.
Eggleton and Tokovinin (2008) list Delta Sagittarii as a binary star system consisting of an evolved K-type giant star with a stellar classification of K3 III, and a white dwarf companion. The giant is a weak barium star, most likely having had its surface abundance of s-process elements enhanced through mass transfer from its orbiting companion. It has an estimated 3.21 times the mass of the Sun and is about 260 million years old.
Delta Sagittarii has three dim visual companions:
- a 14th magnitude star at a separation of 26 arcseconds,
- a 15th magnitude star at a separation of 40 arcseconds, and
- a 13th magnitude star at a separation of 58 arcseconds from the primary.
It bore the traditional names Kaus Media, Kaus Meridionalis, and Media, which derive from the Arabic قوس (qaws, meaning "bow") and Latin media (meaning "middle"). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) 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 Kaus Media for this star.
In Chinese, 箕 (Jī), meaning Winnowing Basket, refers to an asterism consisting of Delta Sagittarii, Gamma Sagittarii, Epsilon Sagittarii and Eta Sagittarii. Consequently, Delta Sagittarii itself is known as 箕宿二 (Jī Sù èr, English: the Second Star of Winnowing Basket.)
In the Hindu system of astrology, this star is also called Purvashada Nakshatra.
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