ζ Cassiopeiae is found just south of the W asterism
Epoch J2000 Equinox J2000
|Right ascension||00h 36m 58.28419s|
|Declination||+53° 53′ 48.8673″|
|Apparent magnitude (V)||3.66 (3.59 - 3.68)|
|U−B color index||–0.89|
|B−V color index||–0.19|
|Radial velocity (Rv)||2.0 km/s|
|Proper motion (μ)||RA: 17.38 mas/yr
Dec.: –9.86 mas/yr
|Parallax (π)||5.50 ± 0.16 mas|
|Distance||590 ± 20 ly
(182 ± 5 pc)
|Absolute magnitude (MV)||–2.8|
|Surface gravity (log g)||3.81 cgs|
|Metallicity [Fe/H]||–0.23 dex|
|Rotational velocity (v sin i)||17 ± 3 km/s|
Zeta Cassiopeiae (ζ Cas, ζ Cassiopeiae) is a star in the constellation Cassiopeia. It has a blue-white hue and is classified as a B-type subgiant with an apparent magnitude of +3.66. It is approximately 590 light years from Earth.
ζ Cas is B2 subgiant, indicating that it has exhausted its core hydrogen and started to evolve away from the main sequence. It has a temperature of over 20,000 K, is about eight times the mass of the sun, and is 5,500 times as luminous.
ζ Cas is a probable member of an unusual group of variable stars known as "Slowly Pulsating B" (SPB) stars. It shows a pulsation frequency of 0.64 per day (or once every 1.56 days) and displays a weak magnetic field with a strength of roughly 3.35 × 10−2 T, which varies with a period of 5.37 days. This likely matches the rotation rate of the star, which, when combined with the low projected rotational velocity, indicates the star may be seen nearly pole-on. Zeta Cassiopeiae is a candidate magnetic Bp star that shows an overabundance of helium. The star contains a randomly oriented fossil magnetic field, which impacts the outflow of the stellar wind. Collisions between streams from this stellar wind creates a shock front, with cooling particles settling toward a co-rotating disk.
In Chinese astronomy, Zeta Cassiopeiae is called 附路, Pinyin: Fùlù, meaning Auxiliary Road, because this star is marking itself and stand alone in Auxiliary Road asterism, Legs (mansion) (see : Chinese constellation). 附路 (Fùlù) is westernized into Foo Loo, but the name Foo Loo was designated not only for Zeta Cassiopeiae, but also for η Cassiopeiae (Achird) by R.H. Allen, with the meaning is "a by-path" 
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