| U Cephei | |
| Planets: | 0 |
| Constellation: | Cepheus |
| Ascension: | 01h 02m 18.34 |
| Declination: | +81° 52` 32.1 |
| Distance: | 825.73 ly (253.16 pc) |
| Eccentricity: | 0.07560 |
| Epoch: | J2000 |
| Magnitude: | 6.9 |
| Spectral: | G8III |
U Cephei is an eclipsing binary star discovered in 1880.[1] [2] It consists of a blue-white main sequence star of spectral type B7Ve that is eclipsed every two and a half days by a less bright giant of type G8III-IV. The drop in brightness lasts 4 hours and the system sees its apparent magnitude increase from 6.7 to 9.2. The total eclipse then lasts 2 hours before an increase in brightness for 4 hours. The two stars, separated by less than 10000000km (10,000,000miles), exchange matter. This transfer towards the blue giant caused the system's orbital period to lengthen by 4 minutes during the 20th century. U Cephei is one of the brightest eclipsing binaries. Located near the north celestial pole, it can be monitored continuously with a 60 millimeter telescope.[3]
The system has two visual companions listed in the double and multiple star catalogs. U Cephei B is a twelfth magnitude star that, as of 2016, was located at an angular distance of 13.9 arcseconds and at a position angle of 63° from U Cephei A. It exhibits a common proper motion with the system, which indicates that it is physically linked to it. U Cephei C is another twelfth magnitude star, but it is only a purely optical double and its proximity to the system is a coincidence.[4]