NGC 2022
Template:Short description Template:Infobox nebula
NGC 2022 is a planetary nebula in the equatorial constellation of Orion, located at a distance of Script error: No such module "convert". from the Sun.[1] 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.[2] 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,[3] an apparent size of Script error: No such module "val"., and a halo extending out to Script error: No such module "val"., which is about the angular diameter of Jupiter as seen from Earth.[4]
This is a double-shell planetary nebula with a wind-compressed inner shell and a more nebulous second shell.[5] The linear radius of the inner shell is estimated at Script error: No such module "convert".. It is expanding with a velocity of Script error: No such module "val".. The second shell is nearly circular and is expanding more slowly than the inner.[6] The mass of the ionized elements in the planetary nebula is Script error: No such module "val"., or 19% of the Sun's mass.[6] A faint outer halo consists of the remains of material ejected during the central star's asymptotic giant branch stage.[7]
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.[4] The central star of this nebula has a visual magnitude of 15.92, a temperature of Script error: No such module "val"., and is radiating 852 times the luminosity of the Sun from a photosphere that has only 6.55% of the Sun's radius.[4]
Gallery
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NGC 2022 taken at the Mount Lemmon SkyCenter (Tucson, AZ) using the 0.8m Schulman Telescope. Image courtesy Adam Block.
References
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