30 Ophiuchi

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]

30 Ophiuchi

Location of 30 Ophiuchi (circled)
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]