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Beta Cephei (Alfirk)

Beta Cephei A or Alfirk A is the prototype of a class of subgiants, which pulsate relatively quick, but weak. Alfirk A changes every 4.57 hours its luminosity for 0.07 magnitudes. Such a change isn't visible to the naked eye.
The blue star has two smaller, white stars as companions.

Constellation: Cepheus
Distance: 595 light-years
Space between Beta Cephei A and B: 45 AU
Orbit period of Beta Cephei A and B: 90 years
Space between Beta Cephei A and C: 2400 AU
Orbit period of Beta Cephei A and C: 30 000 years

Alfirk A

Spectral class: B2
Visual magnitude: 3.23
Luminosity: 14 600 * Sun
Mass: 12 * Sun

Alfirk B

Spectral class: A

Alfirk C

Spectral class: A

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    Beta Cephei
Photo: ESO Online Digitized Sky Survey (negative)

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