Star in the constellation Cepheus
Properties.
Beta Cephei is a triple star comprising a spectroscopic binary with a magnitude 8 optical companion. Its magnitude varies between +3.16 and +3.27 with a period of 0.19048 days.
Beta Cephei Aa is a blue subgiant star with a stellar classification of B1 IV. It has previously been classified with either a main sequence or giant luminosity class. This star has a radius that has been estimated at 7.2 R☉ and a mass of 7 M☉. Other sources have given higher masses on the order of 12 M☉. Like most high-mass B-class stars, Beta Cephei Aa is a relatively young star with an estimated age of just a few million years. Like the majority of giant stars, it rotates slowly on its axis with a rotational velocity of 7 deg/day, a speed which takes the star approximately 51 days to make one complete revolution.
Beta Cephei Ab is a Be star in an 81-year orbit with the giant primary. It has been resolved using speckle interferometry at a distance of 0.25" in 1972. With a mass of about 5 M☉, it is likely a B-class star with a classification of B6.
B Cephei B is a magnitude 7.8 A2 main sequence star 13.6" distant.
Variability.
Beta Cephei pulsates regularly every 4 hours 34 minutes, producing a variation in its visual brightness of 0.11 magnitudes. It is the prototype of the Beta Cephei class of variables, hot main sequence and giant stars that pulsate analogously to Cepheid variables but with the pulsations driven by iron opacity rather than by helium.
References.
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External links.
 ;indicator name="01-sky-coordinates" ; ;templatestyles src="Template:Sky/styles.css" / ;Coordinates: &amp;show_grid=1&amp;show_constellation_lines=1&amp;show_constellation_boundaries=1&amp;show_const_names=1&amp;show_galaxies=1&amp;img_source=IMG_all 21h 28m 39.60s, +70° 33′ 39.0″ ;/indicator ;