Kappa Ophiuchi
star in the constellation Ophiuchus
Kappa Ophiuchi, Latinized from κ Ophiuchi, is a star in the equatorial constellation Ophiuchus. It is a suspected variable star with an average apparent visual magnitude of 3.20, making it visible to the naked eye and one of the brighter members of this constellation. Based upon parallax measurements made during the Hipparcos mission, it is situated at a distance of around 91.5 light-years (28.1 parsecs) from Earth. The overall brightness of the star is diminished by 0.11 magnitudes due to extinction from intervening matter along the line of sight.
The spectrum of this star matches a stellar classification of K2 III, with the luminosity class of 'III' indicating this is a giant star that has exhausted the hydrogen at its core and evolved away from the main sequence of stars like the Sun. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. It is 19% more massive than the Sun, but the outer envelope has expanded to around 11 times the Sun's radius. With its enlarged size, it is radiating 51 times the luminosity of the Sun from its outer atmosphere at an effective temperature of 4,449 K. This is cooler than the Sun's surface and gives Kappa Ophiuchi the orange-hued glow of a K-type star.
Although designated as a variable star, observations with the Hipparcos satellite showed a variation of no more than 0.02 in magnitude. In designating this as a suspected variable star, it is possible that Kappa Ophiuchi was mistaken for Chi Ophiuchi, which is a variable star.
Begin with the source’s own compact description: “Kappa Ophiuchi” is star in the constellation Ophiuchus. The dossier treats that line as a proposition to test through Kappa, Ophiuchi and star, not as a finished interpretation.
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Vocabulary and entity names are the principal evidence signals here, because they determine the precision of every later search. The source revision retrieved here is dated Sep 12, 2026. The linked authority identifier is Q2520858. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1943.
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This entry incorporates text from “Kappa Ophiuchi” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.