66 Ophiuchi
Star in the constellation Ophiuchus
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66 Ophiuchi is a binary[6] variable star[13] in the equatorial constellation of Ophiuchus. It has the variable star designation V2048 Ophiuchi, while 66 Ophiuchi is the Flamsteed designation. This object is visible to the naked eye as a faint, blue-white hued point of light with a baseline apparent visual magnitude of 4.60.[2] It is located approximately 650 light years away from the Sun based on parallax,[1] but is drifting closer with a radial velocity of −13 km/s.[5] The star has a peculiar velocity of 13.1±3.2 km/s[14] relative to its neighbors.
  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ophiuchus |
| Right ascension | 18h 00m 15.79825s[1] |
| Declination | +04° 22′ 07.0163″[1] |
| Apparent magnitude (V) | 4.60[2] |
| Characteristics | |
| Evolutionary stage | main sequence |
| Spectral type | B2Ve[3] |
| U−B color index | −0.81[2] |
| B−V color index | −0.02[2] |
| Variable type | γ Cas[4] |
| Astrometry | |
| Radial velocity (Rv) | −12.80[5] km/s |
| Proper motion (μ) | RA: +1.23[1] mas/yr Dec.: −12.73[1] mas/yr |
| Parallax (π) | 5.01±0.26 mas[1] |
| Distance | 650 ± 30 ly (200 ± 10 pc) |
| Absolute magnitude (MV) | −2.8 + −0.2[6] |
| Orbit[6] | |
| Period (P) | 23421.1 ± 4.1 d |
| Semi-major axis (a) | 178.36 ± 1.37 mas |
| Eccentricity (e) | 0.142 ± 0.006 |
| Inclination (i) | 75.90 ± 0.69° |
| Longitude of the node (Ω) | 338.87 ± 0.31° |
| Periastron epoch (T) | JD 2452658.5 ± 50.2 |
| Argument of periastron (ω) (secondary) | 115.24 ± 0.95° |
| Details | |
| 66 Oph A | |
| Mass | 9.6[6] M☉ |
| Luminosity | 1524.63[7] L☉ |
| Surface gravity (log g) | 3.69[8] cgs |
| Temperature | 22,000[9] K |
| Metallicity [Fe/H] | 0.00[8] dex |
| Rotational velocity (v sin i) | 250[10] km/s |
| Age | 14.0±3.2[11] Myr |
| 66 Oph B | |
| Mass | 3.8[6] M☉ |
| Other designations | |
| 66 Oph, V2048 Oph, BD+04°3570, GC 24500, HD 164284, HIP 88149, HR 6712, SAO 123005, WDS J18003+0422AB[12] | |
| Database references | |
| SIMBAD | data |
The primary star, known as 66 Ophiuchi A, is a main sequence Be star with a stellar classification of B2Ve.[3] Be stars are rapidly rotating stars that eject gas from their equators due to their rotation, forming disks that produce emission lines. 66 Ophiuchi A's disk extends out to 115 R☉.[15] Like many other Be stars, it is a γ Cas variable; a shell star with a circumstellar disc of gas and is exhibiting irregular changes in brightness, ranging from 4.85 up to 4.55 magnitude.[4] The star is 14 million years old with 9.6[6] times the Sun's mass and is spinning rapidly with a projected rotational velocity of 250 km/s.[10] It is radiating 1,525[7] times the Sun's luminosity from its photosphere at an effective temperature of 22,000 K.[9] Because of its rotation, it has a polar equatorial radius 4.50 that of the Sun, but an equatorial radius 5.11 that of the Sun.[15]
A magnitude 6.5 visual companion at an angular separation of 0.1″ has been reported, and is known as 66 Ophiuchi B.[16] It is 2.61 magnitudes fainter than the primary. This corresponds to a mass of about 3.8 times that of the Sun, and a spectral class of about B8.[6]