δ Cephei

Delta Cephei is one of the most significant variable stars, the prototype of what are called "Cepheid variables".
    Through studies on the periods of the variability of Cepheid stars, it has been possible to more accurately gauge distances to outlying galaxies.

To the careful observer the change in magnitude is noticeable. Delta Cephei varies from 3.5 to 4.4 every 5 days 8 hours 47 minutes 31.9 seconds. Compare its magnitude with zeta Cephei, in the same field of vision. Zeta has a magnitude of 3.4. Thus delta will be equal to zeta at its maximum, while noticeably dimmer at its minimum.

Delta Cephei is due east of mu Cephei, one binocular field. It is a multiple star system (BU 702), with most of the components very dim; one component however is a binocular double:
      AC: 4.2, 6.1; 191º, 40.6"

Krüger 60 is very close to delta, about half a degree to the south. This is one of the nearest visual binaries to the Solar System at 13.15 light years away. Both the primary and its companion are red dwarfs. The system is vast, with over 15 components, most between 10 and 14 visual magnitude.
      AB: 9.9, 11.4; 326º, 1.4". The companion orbits every 44.6 years in a nearly circular orbit.
      AI: 9.9, 8.3; 120º, 237.6"

Two more binary systems are in this field of view: 15 Cep (Otto Struve 461) and Struve 2872:
     Otto Struve 461 is a multiple (A-BG) with two very wide companions:
         AD: 6.7, 7.9; 72º, 184"
         AE: 6.7, 7.0; 37º, 237".
     Struve 2872, near the centre of the field of view, is also a multiple system, with one accessible companion:
      AC 7.1, 8.0; 316º, 21.6".

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