30 Ophiuchi
30 Ophiuchi is a single star in the equatorial constellation of Ophiuchus, and figures 0.99° east (specifically E½S) of the heart of cluster Messier 10. It is visible to the naked eye as a faint, orange-hued point of light with an apparent visual magnitude of 4.82. The distance to this star is approximately 350 light years based on parallax. Its present motion is, net, one of approaching rather than parting, at −6.7 km/s, its "radial velocity".
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ophiuchus |
| Right ascension | 17h 01m 03.60142s |
| Declination | −4° 13′ 21.5308″ |
| Apparent magnitude (V) | 4.82 |
| Characteristics | |
| Spectral type | K4III |
| U−B color index | +1.80 |
| B−V color index | +1.48 |
| Astrometry | |
| Radial velocity (Rv) | −6.70 km/s |
| Proper motion (μ) | RA: −39.13 mas/yr Dec.: −78.09 mas/yr |
| Parallax (π) | 9.3138 ± 0.1676 mas |
| Distance | 350 ± 6 ly (107 ± 2 pc) |
| Absolute magnitude (MV) | −0.65 |
| Details | |
| Radius | 35.89+0.54 −2.12 R☉ |
| Luminosity | 299.8±6.2 L☉ |
| Surface gravity (log g) | 1.73 cgs |
| Temperature | 4,009.00+126.67 −29.67 K |
| Metallicity [Fe/H] | −0.03 dex |
| Rotational velocity (v sin i) | 1.4 km/s |
| Other designations | |
| Database references | |
| SIMBAD | data |
This is an aging giant star with a stellar classification of K4III, having exhausted the supply of hydrogen at its core and expanded to 36 times the Sun's radius. It is a suspected variable star. The star is radiating 300 times the luminosity of the Sun from its swollen photosphere at an effective temperature of 4,009 K. It is emitting a far infrared excess due to circumstellar dust, which extends out to a diameter of 240 AU and has a mass of 62×1025 g.
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″).