Delta Sagittarii

Delta Sagittarii

Location of δ Sagittarii (circled)
Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Sagittarius
Right ascension	18h 20m 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[1] mas
Distance	348 ± 7 ly (107 ± 2 pc)
Absolute magnitude (MV)	−1.99[5]
Details
Mass	3.35 ± 0.34[6] M☉
Radius	129[6] R☉
Luminosity	2,500[6] L☉
Surface gravity (log g)	0.74 ± 0.10[6] cgs
Temperature	3,600 ± 300[6] K
Other designations
Kaus Media, Kaus Meridionalis, Media, δ Sagittarii, δ Sgr, Delta Sgr, 19 Sagittarii, CCDM J18210-2950A, CPD-30 5513, FK5 687, GC 25024, HD 168454, HIP 89931, HR 6859, IDS 18146-2952 A, PPM 268275, SAO 186681, WDS J18210-2950A.[7]

Delta Sagittarii (Delta Sgr, δ Sagittarii, δ Sgr) is a double star^[7] in the southern zodiac constellation of Sagittarius. It has the traditional names Kaus Media, Kaus Meridionalis, and Media.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 Earth.^[1]

This is a giant star with a stellar classification K3 III. It has a mass of about 3.4 times that of the Sun, while the outer envelope has expanded to 129 times the Sun's radius. With an effective temperature of roughly 3,600 K, it is radiating 2,500 times the luminosity of the Sun.^[6]

It has three dim companions:^{[citation needed]}

• 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 is not certain that these stars form a physical system or whether they are merely aligned by chance.

Name and etymology

• The names Kaus Media, Kaus Meridionalis, and Media, are come from the Arabic قوس qaws 'bow' and Latin media 'middle'.
• This star, together with :
  • γ Sgr, ε Sgr, ζ Sgr, λ Sgr, σ Sgr, τ Sgr and φ Sgr, consisting the asterism Teapot.^[8][9]
  • γ Sgr, ε Sgr and η Sgr were Al Naʽām al Wārid (النعم الوارد), the Going Ostriches.^[10]
  • γ Sgr and ε Sgr were Akkadian Sin-nun‑tu, or Si-nu-nu‑tum, the Swallow.^[10]
• In Chinese, 箕 (Jī), meaning Winnowing Basket, refers to an asterism consisting of δ Sagittarii γ Sagittarii, ε Sagittarii and η Sagittarii. Consequently, δ Sagittarii itself is known as 箕宿二 (Jī Sù èr, English: the Second Star of Winnowing Basket.)^[11]
• In the Hindu system of astrology, this star is also called "Purvashada Nakshatra".

See also

• Delta Sagittarii in fiction

References

External links

• Kaus Media