The object is a multi-shell planetary nebula with a bright inner nebula with a diameter of60″, consisting of two somewhat detached shells.[6] It is expanding with a velocity of37 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 of130″.[7] The mass of the main nebula is estimated at0.45 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 theasymptotic 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.
