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The location of 63 Ophiuchi (circled) in the constellation Sagittarius |
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| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) |
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|---|---|
| Constellation | Sagittarius |
| Right ascension | 17h 54m 54.04380s[1] |
| Declination | −24° 53′ 13.5413″[1] |
| Apparent magnitude (V) | 6.18[2] |
| Characteristics | |
| Spectral type | O8III[2] |
| U−B color index | –0.89[3] |
| B−V color index | +0.04[3] |
| Astrometry | |
| Radial velocity (Rv) | –11[4] km/s |
| Proper motion (μ) | RA: 1.66[1] mas/yr Dec.: –2.63[1] mas/yr |
| Parallax (π) | −0.77 ± 0.40[2] mas |
| Distance | approx. -4000 ly (approx. -1300 pc) |
| Details | |
| Rotational velocity (v sin i) | 86[5] km/s |
| Other designations | |
63 Ophiuchi is an O-type giant star in the constellation Sagittarius, despite its name. During a 2009 survey for companions of massive stars, it was observed using speckle interferometry but no companion was found.[6] Uncertain negative parallax measurements of –0.77 ± 0.40 mas[2] suggest that this extremely luminous star may be located about 4000 light-years away. An estimate of the distance based on the strength of the Ca II line yields a more modest value of 2,605 ly (799 pc).[7] The star lies only 0.3° north of the galactic plane.[2]
In 1983, astronomers from the Sternberg Astronomical Institute in Moscow, Russia identified a faint, shell-shaped nebula surrounding the star that was being excited by the star's energy. Named Sharpless 22, this ring-shaped nebula has a double-shell structure with an inner envelope spanning 45–50′ (9–18 pc), surrounded by a diffuse envelope some 65–80′ (14–29 pc) across. At an estimated mass loss rate of (6–8) × 10–6 M☉/yr, it would take the star about (1–5) × 105 years to produce such a nebula from the outflow of its stellar wind.[8]
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