||The prototype of classical Cepheid variables, which is a pulsating yellow supergiant.
John Goodricke was the first in 1784 to discover its variability. The star shows a
quick and sharp rise from minimum to maximum, and slowly declines to its minimum again.
The changes in brightness are accompanied by and principally caused by changes in
stellar temperature and also by changes in radius. δ Cephei was actually the second
Cepheid variable to be discovered. The first one, Eta Aquilae, had been discovered
earlier the same year by Edward Pigott. δ Cephei varies with a period of 5.366341
days (or 5 days 8 hours 37.5 minutes) from magnitude 3.48, spectral type F5 Ib in
its maximum to magnitude 4.37, spectral type G2 Ib in its minimum. It lies at a distance
of 1,340 light-years.