At this distance, the visual magnitude of the star is diminished by 0.23 as a result of extinction caused by gas and dust along the line of sight.

[15] Because the period of this class of variable is dependent on the star's luminosity, Delta Cephei is of particular importance as a calibrator for the period-luminosity relationship, since its distance is now one of the most precisely established for a Cepheid.

[6] Hence, in 2002, the Hubble Space Telescope was used to determine the distance to Delta Cephei within a 4% margin of error: 273 parsecs (890 light-years) .

[17] However, a re-analysis of Hipparcos data found a larger parallax than before, leading to a shorter distance of 244 ± 10 pc, which is equivalent to 800 light-years.

The result of this expelled gas is the formation of a nebula about 1 parsec across, centered on Delta Cephei, and containing 0.07–0.21 solar masses of neutral hydrogen.

It is heating the matter being ejected by the stellar wind of Delta Cephei, causing the surrounding circumstellar material to emit infrared radiation.