The object is a multi-shell planetary nebula with a bright inner nebula with a diameter of 60″, consisting of two somewhat detached shells.[6] It is expanding with a velocity of 37 km/s.[7] The structure is surrounded by a fainter, mostly circular halo that is more visible on the western half,[6] and has a diameter of 130″.[7] The mass of the main nebula is estimated at 0.45 M☉, while the shell has 0.5–0.8 M☉.[6] The main nebula has a temperature of about 10–13,000 K, rising to 15–17,000 K at the inner edge.[8]
The nebula consists of material ejected from the central star during the asymptotic giant branch stage, beginning about 8,500 years ago. The main nebula was formed at about half that age.[7] The central star of this planetary nebula is a 17.7-magnitudewhite dwarf,[3] with a surface temperature of about 75,000 K (74,700 °C).[9]
^ abcCorradi, R. L. M.; et al. (February 2000). Manchado, A.; Stanghellini, L.; Schoenberner, D. (eds.). "A hydrodynamical study of multiple-shell planetaries . I. NGC 2438". Astronomy and Astrophysics. 354: 1071–1085. Bibcode:2000A&A...354.1071C.
^Dalnodar, Silvia (August 2012). The ionization state of the halo planetary nebula NGC 2438. Planetary Nebulae: An Eye to the Future, Proceedings of the International Astronomical Union, IAU Symposium. Vol. 283. pp. 338–339. arXiv:1109.5609. Bibcode:2012IAUS..283..338D. doi:10.1017/S1743921312011313.