10 Lacertae
star in the constellation Lacerta
10 Lacertae (10 Lac) is a star in the constellation Lacerta. With an apparent magnitude of 4.9, it is located around 550 parsecs (1,800 ly) distant in the small Lacerta OB1 association. It is a hot blue main-sequence star of spectral type O9V, a massive star that is currently fusing its core hydrogen. It is a suspected Beta Cephei variable star.
It was one of the first O-type stars (along with S Monocerotis) to be defined as an anchor point for the MKK spectral classification; since the early twentieth century it has served as such a point. Specifically, the star is representative of O9V stars, meaning relatively cool O-type stars on the main-sequence.
It is the star with the smallest angular diameter measured by the CHARA array as of 2018, at 0.11±0.02 milliarcseconds.
10 Lacertae has an 8th magnitude companion about one arc-minute away.
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This entry incorporates text from “10 Lacertae” 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.