Kappa Cassiopeiae

Lore & Background

Kappa Cassiopeiae is a member of the Cassiopeia OB14 stellar association (Cas OB14), though its distance from Gaia parallax measurement is about 1400 pc. Its spectrum is unusual, showing anomalously weak nitrogen lines, taken as an actual nitrogen deficiency in the atmosphere. The modified letter C in its classification indicates an assumption that it is also carbon-rich, although this might not actually be the case. It is interpolated to BC0.7, being slightly hotter than a standard B1 star.

Classified as an Alpha Cygni type variable star, its brightness varies by a few hundredths of a magnitude. Periods of two hours, 2.65 days, and nine days have been reported from observations at different times. It is a runaway star, and its magnetic field and wind of particles create a visible bow shock 4 light-years ahead of it, colliding with diffuse interstellar gas and dust. The bow shock is about the same distance that Earth is from Proxima Centauri, and its dimensions are vast: around 12 light-years long and 1.8 light-years wide.

In Chinese astronomy, κ Cassiopeiae is associated with an asterism representing a legendary charioteer from the Spring and Autumn period. It was originally identified as the charioteer's whip, but this name was later transferred to γ Cassiopeiae, with κ Cassiopeiae becoming one of the charioteer's four horses. The IAU Working Group on Star Names approved the name Cexing for κ Cassiopeiae on 13 November 2025, and it is now so entered in the IAU Catalog of Star Names; xing means star, and this form of the name was already used in ancient times.

Reader's Guide

Kappa Cassiopeiae holds significance as a runaway star whose motion through space produces a dramatic bow shock, one of the few such structures visible from Earth. This bow shock, extending 12 light-years long and 1.8 light-years wide, provides a direct window into the interaction between a massive star's wind and the interstellar medium. Its unusual spectrum, with anomalously weak nitrogen lines and a possible carbon enrichment, challenges standard stellar classification and suggests an atypical chemical composition. As an Alpha Cygni type variable, its brightness variations on multiple timescales offer insights into the pulsational behavior of hot supergiants. The star's membership in the Cassiopeia OB14 association ties it to a region of recent star formation, while its Chinese heritage—first as the charioteer's whip, then as one of four horses—connects it to ancient astronomical traditions. The official naming Cexing by the IAU in 2025 formalizes this cultural link, preserving a name already used in antiquity. Its visibility to the naked eye as a 4th magnitude star makes it accessible to amateur observers, while its scientific peculiarities continue to attract professional study.