[4] Radiation from the star causes the shed outer layer to heat to about 10,000 degrees Celsius and become visible as a planetary nebula.

[4] About 30,000 years from now, scientists theorize that NGC 40 will fade away, leaving only a white dwarf star approximately the size of Earth.

[4] Morphologically, the shape of NGC 40 resembles a barrel with the long axis pointing towards the north-northeast.

[5] The central star of NGC 40 has a Henry Draper Catalogue designation of HD 826.

[6] It has a spectral type of [WC8], indicating a spectrum similar to that of a carbon-rich Wolf–Rayet star.