Tags: Star.
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 2605 ly (799 pc).
