NGC 2022

NGC 2022 is a planetary nebula in the equatorial constellation 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]

NGC 2022

Emission nebula
Planetary nebula
NGC 2022 taken by HST.[1]
Observation data: J2000 epoch
Right ascension	05h 42m 06.19056s[2]
Declination	+09° 05′ 10.5843″[2]
Distance	8.21 kly (2.518 kpc)[3] ly
Apparent magnitude (V)	11.6[4]
Apparent dimensions (V)	28″[4]
Constellation	Orion
Physical characteristics
Radius	0.326 ± 0.039 ly[5] ly
Notable features	Double-shell
Designations	PK 196-10 1, IRAS 05393+0903[6]
See also: Lists of nebulae

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]

Gallery

• 
  A Hubble Space Telescope (HST) image of NGC 2022. Credit: HST/NASA/ESA.
• 
  NGC 2022 taken at the Mount Lemmon SkyCenter (Tucson, AZ) using the 0.8m Schulman Telescope. Image courtesy Adam Block.