U Cephei

Natural : variable star
Distance : 554 al
Magniude : 6.6
apparent Diameter : no
Coordinated : AD=1h2min, Visible D=81°54'
with binoculars

This Binary with eclipse S.A. discovered in 1880. It is composed of a star of the type B which is eclipsed every two days and half by a Géante of the type G, less brilliant but larger. Result: the fall of Luminosité, which lasts 4 hours, is spectacular; its Magnitude passes from 6.7 to 9.2. The total eclipse lasts then 2 hours before an increase of 4 hours luminosity. Both Star S, separated by less than 10 million km, exchange Matière. This transfer in direction of the blue giantess made that the orbital Period system lengthened 4 minutes during the XXème century. U Cephei is one of most brilliant binary with eclipses. Located close to the celestial north pole, it can be followed permanently with a Lunette of 60 mm (even if, at the time of the minima, it is hardly any more visible with the Oculaire).

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