Kappa Cassiopeiae

κ Cassiopeiae
Location of κ Cassiopeiae (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cassiopeia
Right ascension 00h 32m 59.991s[1]
Declination +62° 55′ 54.42″[1]
Apparent magnitude (V) 4.12 - 4.21[2]
Characteristics
Spectral type BC0.7 Ia[3]
Apparent magnitude (U) 3.50[4]
Apparent magnitude (B) 4.276[4]
Apparent magnitude (J) 4.141[4]
Apparent magnitude (H) 4.148[4]
Apparent magnitude (K) 4.013[4]
U−B color index −0.776[4]
B−V color index +0.0869[4]
J−H color index −0.0069[4]
J−K color index +0.128[4]
Variable type α Cyg[5]
Astrometry
Radial velocity (Rv)0.30[6] km/s
Proper motion (μ) RA: +3.65[1] mas/yr
Dec.: −2.07[1] mas/yr
Parallax (π)0.73 ± 0.17 mas[1]
Distanceapprox. 4,000 ly
(approx. 1,400 pc)
Absolute magnitude (MV)−7.1[7]
Details
Mass33[8] M☉
Radius39[7] R☉
Luminosity490,000[7] L☉
Surface gravity (log g)2.79[7] cgs
Temperature24,600[7] K
Rotational velocity (v sin i)58[7] km/s
Age4.5[9] Myr
Other designations
15 Cassiopeiae, HR 130, HD 2905, BD+62°102, FK5 16, HIP 2599, SAO 11256, GC 645
Database references
SIMBADdata
Kappa Cassiopeiae and its bow shock. Spitzer infrared image (NASA/JPL-Caltech)

Kappa Cassiopeiae (κ Cas, κ Cassiopeiae) is a star in the constellation Cassiopeia.

κ Cassiopeiae has an unusual spectrum that has anomalously weak nitrogen lines, taken as an actual nitrogen deficiency in the atmosphere. This is indicated by the modified letter C on the assumption that it is also carbon-rich, although this might not actually be the case.[8] It is also interpolated to BC0.7, being slightly hotter than a standard B1 star.[10][11]

κ Cassiopeiae is assumed to be a member of the Cassiopeia OB14 stellar association (Cas OB14) and treated as being at a distance of about 1,100 pc,[11] while its distance found from the Hipparcos parallax is about 1,400 parsecs.[1] Its Gaia parallaxes are somewhat uncertain due to the brightness of the star, but a modern determination of the distance to Cas OB14 is 880 pc.[12]

A light curve for Kappa Cassiopeiae, plotted from Hipparcos data[13]

It is classified as an Alpha Cygni type variable star and its brightness varies by a few hundredths of a magnitude. Periods of two hours,[14] 2.65 days,[15] and nine days[16] have been reported from observations at different times.

It is a runaway star. Its magnetic field and wind of particles creates a visible bow shock 4 light-years ahead of it, colliding with the diffuse, and usually invisible, interstellar gas and dust. This is about the same distance that Earth is from Proxima Centauri, the nearest star to the Sun.[17] The dimensions of the bow shock are vast: around 12 light-years long and 1.8 light-years wide.[18]

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