| |
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Sagittarius |
| Right ascension | 18h20m 59.64354s[1] |
| Declination | −29° 49′ 41.1659″[1] |
| Apparent magnitude (V) | +2.70[2] |
| Characteristics | |
| Spectral type | K3 III[3] |
| U−B color index | +1.55[2] |
| B−V color index | +1.38[2] |
| Astrometry | |
| Radial velocity (Rv) | –19.9[4] km/s |
| Proper motion (μ) | RA: +32.54[1] mas/yr Dec.: −25.57[1] mas/yr |
| Parallax (π) | 9.38 ± 0.18 mas[1] |
| Distance | 348 ± 7 ly (107 ± 2 pc) |
| Absolute magnitude (MV) | −1.99[5] |
| Details | |
| δ Sgr A | |
| Mass | 3.21[6] M☉ |
| Radius | 76.84[6][a] R☉ |
| Luminosity | 1,660[6] L☉ |
| Surface gravity (log g) | 0.30[7] cgs |
| Temperature | 4,203±69[6] K |
| Metallicity [Fe/H] | −0.32[7] dex |
| Rotational velocity (v sin i) | 3.6[8] km/s |
| Age | 260[6] Myr |
| Other designations | |
Kaus Media, Kaus Meridionalis, Media, δ Sgr, CPD−30°5513, FK5 687, GC 25024, HD 168454, HIP 89931, HR 6859, SAO 186681, PPM 268275, CCDM J18210-2950A, WDS J18210-2950A[9] | |
| Database references | |
| SIMBAD | Delta Sagittarii |
Delta Sagittarii (δ Sagittarii, abbreviated Delta Sgr, δ Sgr), formally named Kaus Media /ˌkɔːs ˈmiːdiə/,[10][11] is a star in the southern zodiac constellationofSagittarius. The apparent visual magnitude of this star is +2.70,[2] making it easily visible to the naked eye. Parallax measurements place the distance at roughly 348 light-years (107 parsecs) from the Sun.[1]
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,[3] and a white dwarf companion.[12] The giant is a weak barium star, most likely having had its surface abundance of s-process elements enhanced through mass transfer from an orbiting companion, presumed to be a white dwarf.[13] It has an estimated 3.21 times the mass of the Sun and is about 260 million years old.[6]
Delta Sagittarii has three dim visual companions:[14]
δ Sagittarii (LatinisedtoDelta Sagittarii) is the star's Bayer designation.
It bore the traditional names Kaus Media, Kaus Meridionalis, and Media, which derive from the Arabic: قوس qaws ('bow') and Latin: media ('middle'). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[15] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[16] included a table of the first two batches of names approved by the WGSN; which included Kaus Media for this star.
In the catalogue of stars in the CalendariumofAl Achsasi al Mouakket, this star was designated Thani al Waridah, meaning 'second of Warida'.[17]
InChinese astronomy, 箕 Jī ('Winnowing Basket') refers to an asterism consisting of Delta Sagittarii, Gamma2 Sagittarii, Epsilon Sagittarii and Eta Sagittarii. Consequently, the Chinese name for Delta Sagittarii itself is 箕宿二 Jī Sù èr ('the Second Star of Winnowing Basket').[18]
This star, together with Gamma Sagittarii, Epsilon Sagittarii, Zeta Sagittarii, Lambda Sagittarii, Sigma Sagittarii, Tau Sagittarii and Phi Sagittarii, comprises the Teapot asterism.[19]
InHindu astrology, this star is also called Purvashada Nakshatra.
