30 Ophiuchi
Star in the constellation Ophiuchus
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30 Ophiuchi is a single[11] star in the equatorial constellation of Ophiuchus, and figures 0.99° east (specifically E½S) of the heart of cluster Messier 10.[12] It is visible to the naked eye as a faint, orange-hued point of light with an apparent visual magnitude of 4.82.[2] The distance to this star is approximately 350 light years based on parallax.[7] Its present motion is, net, one of approaching rather than parting, at −6.7 km/s, its "radial velocity".[6]
 | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ophiuchus |
| Right ascension | 17h 01m 03.60142s[1] |
| Declination | −04° 13′ 21.5308″[1] |
| Apparent magnitude (V) | 4.82[2] |
| Characteristics | |
| Spectral type | K4III[3] |
| U−B color index | +1.80[4] |
| B−V color index | +1.48[4] |
| Variable type | none[5] |
| Astrometry | |
| Radial velocity (Rv) | −6.70[6] km/s |
| Proper motion (μ) | RA: −39.13[7] mas/yr Dec.: −78.09[7] mas/yr |
| Parallax (π) | 9.3138±0.1676 mas[1] |
| Distance | 350 ± 6 ly (107 ± 2 pc) |
| Absolute magnitude (MV) | −0.65[2] |
| Details | |
| Radius | 35.89+0.54 −2.12[1] R☉ |
| Luminosity | 299.8±6.2[1] L☉ |
| Surface gravity (log g) | 1.73[8] cgs |
| Temperature | 4,009.00+126.67 −29.67[1] K |
| Metallicity [Fe/H] | −0.03[2] dex |
| Rotational velocity (v sin i) | 1.4[9] km/s |
| Other designations | |
| 30 Oph, NSV 8111, BD−04°4215, FK5 1445, GC 22937, HD 153687, HIP 83262, HR 6318, SAO 141483, CCDM J17011-0413A, WDS J17011-0413A[10] | |
| Database references | |
| SIMBAD | data |
This is an aging giant star with a stellar classification of K4III,[3] having exhausted the supply of hydrogen at its core and expanded to 36[1] times the Sun's radius. The star is radiating 300[1] times the luminosity of the Sun from its swollen photosphere at an effective temperature of 4,009 K.[1] It is emitting a far infrared excess due to circumstellar dust,[13] which extends out to a diameter of 240 AU and has a mass of 62×1025 g.[14]
The primary presents with two visual companions: B, at magnitude 9.71 and separation 99.8″, and C, at magnitude 8.75 and separation 220.9″ (3′ 40.9″).[15]