2000 L ☉
Delta Cephei is a variable star in the constellation Cepheus, whose variability was discovered in 1784 by the English astronomer John Goodricke.
Delta Cephei is a yellow supergiant, the ( 887 light years ) is located at a distance of 272 parsecs from the sun. Its apparent brightness varies with a period of 5.36643 days between 3.48 m and 4.37 m, which also changes its spectral between F5Ib and G2Ib. Thus, a periodic change of the surface temperature to about 1000 ° is connected.
Delta Cephei is the prototype of a class of pulsating variables stars, the so-called Delta Cephei stars, which - as its period depends only on the luminosity - in the distance measurement of galaxies plays a role.
Delta Cephei is also a separable already in prism binocular double star. Its companion star is located at a position angle of 191 degrees 41 ' of Delta Cephei away. He has an apparent magnitude of 6.3 m and belongs to the spectral class B7 on.