Epoch J2000.0 Equinox J2000.0 (ICRS)
|Right ascension||17h 54m 54.04380s|
|Declination||−24° 53′ 13.5413″|
|Apparent magnitude (V)||6.18|
|U−B color index||–0.89|
|B−V color index||+0.04|
|Radial velocity (Rv)||–11 km/s|
|Proper motion (μ)||RA: 1.66 mas/yr
Dec.: –2.63 mas/yr
|Parallax (π)||−0.77 ± 0.40 mas|
|Distance||approx. −4,000 ly
(approx. −1,300 pc)
|Rotational velocity (v sin i)||86 km/s|
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. Uncertain negative parallax measurements of –0.77 ± 0.40 mas 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). The star lies only 0.3° north of the galactic plane.
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.
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