NGC 2022 is a planetary nebula in the equatorialconstellation of Orion, located at a distance of 8.21 kilolight-years from the Sun.[3] It was first observed by William Herschel on December 28, 1785, who described it as: considerably bright, nearly round, like a star with a large diameter, like an ill-defined planetary nebula.[7] In medium-sized amateur telescopes it looks like a small grayish patch of light. It is not very bright but it is still easy to spot it in the eyepiece. Even in a telescope as small as 80mm it can just be seen using a narrowband filter such as an OIII filter as a 'fuzzy' star. The object has the shape of a prolate spheroid with a major to minor axis ratio of 1.2,[4] an apparent size of 28″, and a halo extending out to 40″, which is about the angular diameter of Jupiter as seen from Earth.[8]
This is a double-shell planetary nebula with a wind-compressed inner shell and a more nebulous second shell.[9] The linear radius of the inner shell is estimated at 0.326 ± 0.039 ly. It is expanding with a velocity of 28±2 km/s. The second shell is nearly circular and is expanding more slowly than the inner.[5] The mass of the ionized elements in the planetary nebula is 0.19 M☉, or 19% of the Sun's mass.[5] A faint outer halo consists of the remains of material ejected during the central star's asymptotic giant branch stage.[10]
NGC 2022 lies 11° away from the Galactic Plane, which position suggests it was formed from a low-mass star. The elemental abundances are similar to those in the Sun, although carbon is about 50% higher and sulfur is a factor of two lower.[8] The central star of this nebula has a visual magnitude of 15.92, a temperature of 122,000 K, and is radiating 852 times the luminosity of the Sun from a photosphere that has only 6.55% of the Sun's radius.[8]
^ abcFinlay, Warren H. (2014), Concise Catalog of Deep-sky Objects, The Patrick Moore Practical Astronomy Series (2nd ed.), Springer Science & Business Media, p. 188, ISBN978-3-319-03169-9.
^ abcSabbadin, F.; et al. (July 1984), "The planetary nebulae NGC 1535 and NGC 2022.", Astronomy and Astrophysics, 136: 193–199, Bibcode:1984A&A...136..193S.
^Corradi, R. L. M.; et al. (April 2003), "Ionized haloes in planetary nebulae: new discoveries, literature compilation and basic statistical properties", Monthly Notices of the Royal Astronomical Society, 340 (2): 417–446, Bibcode:2003MNRAS.340..417C, doi:10.1046/j.1365-8711.2003.06294.x.
