74 Ophiuchi
Star in the constellation Ophiuchus
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74 Ophiuchi is a suspected binary star[9] in the equatorial constellation of Ophiuchus, near the border with Serpens Cauda. It is visible to the naked eye as a faint, yellow-hued point of light with a combined apparent visual magnitude of 4.85.[2] The system is located at a distance of 238 light years from the Sun based on parallax,[1] and is drifting further away with a radial velocity of +4.4 km/s.[5]
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ophiuchus |
| Right ascension | 18h 20m 52.06435s[1] |
| Declination | +03° 22′ 37.7817″[1] |
| Apparent magnitude (V) | 4.85[2] |
| Characteristics | |
| Spectral type | G8III[3] |
| U−B color index | +0.61[4] |
| B−V color index | +0.91[4] |
| Astrometry | |
| Radial velocity (Rv) | +4.35[5] km/s |
| Proper motion (μ) | RA: −7.646[1] mas/yr Dec.: +12.546[1] mas/yr |
| Parallax (π) | 13.7320±0.2060 mas[1] |
| Distance | 238 ± 4 ly (73 ± 1 pc) |
| Absolute magnitude (MV) | 0.34[2] |
| Details | |
| Mass | 2.38[6] M☉ |
| Radius | 10.52+0.32 −1.04[1] R☉ |
| Luminosity | 66.0±1.2[1] L☉ |
| Surface gravity (log g) | 2.70[6] cgs |
| Temperature | 5,073+271 −76[1] K |
| Metallicity [Fe/H] | -0.21[6] dex |
| Rotational velocity (v sin i) | 0.0[5] km/s |
| Age | 1.73[7] Gyr |
| Other designations | |
| 74 Oph, BD+03°3680, FK5 1476, GC 25036, GJ 9615 A, HD 168656, HIP 89918, HR 6866, SAO 123377, CCDM J18209+0323A, WDS J18209+0323A[8] | |
| Database references | |
| SIMBAD | data |
The primary member, designated component A, is an aging giant star with a stellar classification of G8III[3] and an estimated age of 1.73[7] billion years. Having exhausted the hydrogen supply at its core, the star has expanded to 10.5[1] times the Sun's radius. It is a red clump giant,[10] which means it is on the horizontal branch and is generating energy through helium fusion at its core. The star has 2.4[6] times the mass of the Sun and is radiating 66[1] times the Sun's luminosity from its swollen photosphere at an effective temperature of around 5,073 K.[1]
The magnitude 11.5 secondary, component B, lies at an angular separation of 28.1″ from the primary, as of 2008.[9] A visual companion, component C, is magnitude 12.28 and has a separation of 57.9″.[11]