Historical view of the Hercules constellation showing the star Sarin (δ Her) next to the Keystone asterism. |
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Observation data Epoch J2000 Equinox J2000 |
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Constellation | Hercules |
Right ascension | 17h 15m 01.9106s[1] |
Declination | 24° 50′ 21.135″[1] |
Apparent magnitude (V) | 3.126[1] |
Characteristics | |
Spectral type | A3IV [1] |
U−B color index | +0.7 [2] |
B−V color index | +0.08[2] |
Astrometry | |
Radial velocity (Rv) | -40.0[1] km/s |
Proper motion (μ) | RA: -21.14[1] mas/yr Dec.: -157.68[1] mas/yr |
Parallax (π) | 43.41 ± 0.15[3] mas |
Distance | 75.1 ± 0.3 ly (23.04 ± 0.08 pc) |
Absolute magnitude (MV) | +1.31 |
Details | |
Mass | 2.0 [4] M☉ |
Radius | 2.0 [4] R☉ |
Luminosity | 18.5 [4] L☉ |
Temperature | 8,500 [4] K |
Metallicity | ? Fe/H |
Rotational velocity (v sin i) | 270 [4] km/s |
Age | 3.7×109 [4] years |
Other designations | |
Database references | |
SIMBAD | data |
Coordinates: 17h 15m 01.910s, +24° 50′ 21.135″
Delta Herculis (δ Her, δ Herculis) is a fourth-magnitude star in the constellation Hercules. It has the traditional name Sarin.[5][6]
In Chinese, 天市左垣 (Tiān Shì Zuǒ Yuán), meaning Left Wall of Heavenly Market Enclosure, refers to an asterism which is represent eleven old states in China which is marking the left borderline of the enclosure, consisting of δ Herculis, λ Herculis, μ Herculis, ο Herculis, 112 Herculis, ζ Aquilae, θ1 Serpentis, η Serpentis, ν Ophiuchi, ξ Serpentis and η Ophiuchi[7]. Consequently, δ Herculis itself is known as 天市左垣一 (Tiān Shì Zuǒ Yuán yī, English: the First Star of Left Wall of Heavenly Market Enclosure), represent the state Wei (魏)[8][9], together with 33 Capricorni (φ Capricorni and χ Capricorni in R.H. Allen's version)[10] in Twelve States (asterism).
In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Menkib al Jathi al Aisr, which was translated into Latin as Humerus Sinister Ingeniculi, meaning the left shoulder of the kneeling man.[11]
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Sarin is a complex star system consisting of at least 2 stars and possibly as many as 5. The main star is an A Type main sequence subgiant with a stellar classification A3IV. The subgiant has both a mass and radius that are roughly two times solar yielding a total luminosity of about 18.5L☉[4] Though it only shines with an apparent magnitude of 3.12, it the third brightest star in the Hercules constellation. The most recent Hipparcos data yields a distance estimate of approximately 23.1 parsecs (pc) from Earth or 75 light years (ly).
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