Location of δ Ophiuchi (middle right) |
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Observation data Epoch J2000 Equinox J2000 |
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Constellation | Ophiuchus |
Right ascension | 16h 14m 20.7395s[1] |
Declination | −03° 41′ 39.563″ |
Apparent magnitude (V) | 2.74[2] |
Characteristics | |
Spectral type | M0.5III[3] |
U−B color index | +1.96[4] |
B−V color index | +1.59[4] |
Astrometry | |
Radial velocity (Rv) | −19.9[5] km/s |
Proper motion (μ) | RA: −45.83[1] mas/yr Dec.: −142.91[1] mas/yr |
Parallax (π) | 19.16 ± 1.02[1] mas |
Distance | 170 ± 9 ly (52 ± 3 pc) |
Details | |
Surface gravity (log g) | 1.4[6] |
Temperature | 3,679[6] K |
Metallicity | [6] |
Other designations | |
Delta Ophiuchi (δ Oph, δ Ophiuchi) is a star in the constellation Ophiuchus. It has the traditional name Yed Prior (and the star Epsilon Ophiuchi, with which it forms a naked eye optical double, is Yed Posterior).
The traditional name Yed is derived from Arabic meaning "the hand", and the two stars are the left hand of Ophiuchus (the Serpent Bearer) that holds the head of the serpent Serpens Caput.
It was a member of the indigenous Arabic asterism al-Nasaq al-Yamānī, "the Southern Line" of al-Nasaqān "the Two Lines".[7] It was a member of indigenous Arabic asterism al-Nasaq al-Yamānī, "the Southern Line" of al-Nasaqān "the Two Lines".[8], along with α Ser (Unukalhai), δ Ser (Qin, Tsin), ε Ser (Ba, Pa), ε Oph (Yed Posterior), ζ Oph (Han) and γ Oph (Tsung Ching).[9]
According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, al-Nasaq al-Yamānī or Nasak Yamani were the title for two stars :δ Ser as Nasak Yamani I and ε Ser as Nasak Yamani II (exclude this star, α Ser, ε Oph, ζ Oph and γ Oph)[10]
In Chinese, 天市右垣 (Tiān Shì Yòu Yuán), meaning Right Wall of Heavenly Market Enclosure, refers to an asterism which is represent eleven old states in China which is marking the right borderline of the enclosure, consisting of δ Ophiuchi, β Herculis, γ Herculis, κ Herculis, γ Serpentis, β Serpentis, α Serpentis, δ Serpentis, ε Serpentis, ε Ophiuchi and ζ Ophiuchi [11]. Consequently, δ Ophiuchi itself is known as 天市右垣九 (Tiān Shì Yòu Yuán jiǔ, English: the Ninth Star of Right Wall of Heavenly Market Enclosure), represent the state Liang (梁) (or Leang)[12][13].
Delta Ophiuchi is 170 light years from Earth, while Epsilon is 108; hence they are a mere optical double. Yed Prior is a red giant (class M) with a temperature of 3,679 K.
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