RW Cephei is a K-type hypergiant and a semirregular variable star in the constellation Cepheus, at the edge of the Sharpless 132 H II region and close to the small open cluster Berkeley 94.

[17][18] The first documented sighting of RW Cephei dates back to 1746 when it was included in a star catalog compiled by James Bradley.

In late 2022, RW Cephei was announced to be undergoing a great dimming event,[16][28][29] and it was subsequently observed by the CHARA interferometry array in December.

[13] The distance to RW Cephei has been estimated on the basis of its spectroscopic luminosity and it is assumed to be a member of the Cepheus OB1 association, placing it within the Perseus Arm of the Milky Way.

[3] RW Cephei has been classified as a semi-regular variable star of type SRd, meaning that it is a slowly varying yellow giant or supergiant.

[16][28][29] It was speculated to be caused by short periods of enhanced mass loss leading to the condensation of dust that partially obscures the stellar photosphere.

[8] This was later confirmed by observations with the CHARA array, revealing a dark patch on the western side of the star suggested to be a dust cloud released in a recent surface mass ejection.

[13] An unusually bright maximum attained in 2019 right before the dimming was suspected to be caused by an energetic convective upwelling of hot gas, later being expelled and cooling into a dust cloud obscuring the star.

[26] A follow-up study in 1972 focusing on redder spectral regions found unusually strong Na D lines too intense to be caused by the interstellar medium.

Images obtained using the SURFING algorithm result in a limb-darkened angular diameter of 2.45 mas, corresponding to a linear radius of 900–1,760 R☉ depending on the adopted distance.

[27][46][8][13] The IRAS low resolution spectrum shows signatures of optically thick silicate emission at 10 and 18 μm,[47] an indication for high amounts of mass loss.

[50] Analysis of the surrounding mid-infrared emission indicates that RW Cephei ended a period of enhanced mass loss ~95–140 years ago,[b] suggesting that it has left the red supergiant phase and is currently evolving towards hotter temperatures.