NGC 2392

NGC 2392, also known as Caldwell 39, Eskimo Nebula, Clown-faced Nebula, and Lion Nebula[4], is a bipolar[5] double-shell[6] planetary nebula (PN). It was discovered by astronomer William Herschel in 1787. The formation resembles a person's head surrounded by a parka hood. It is surrounded by gas that composed the outer layers of a Sun-like star. The visible inner filaments are ejected by a strong wind of particles from the central star. The outer disk contains unusual, light-year-long filaments.

NGC 2392
Emission nebula
Planetary nebula
NGC 2392 by HST in 1999.
Credit: NASA/ESA/STScI
Observation data: J2000 epoch
Right ascension 07h 29m 10.7669s[1]
Declination+20° 54′ 42.488″[1]
Distance6520±560[2] ly
Apparent magnitude (V)10.1[1]
Apparent dimensions (V)48″; × 48″;[3]
ConstellationGemini
Physical characteristics
Radius≥0.34 ly[a] ly
Absolute magnitude (V)≤0.4 [b]
Notable features–
DesignationsNGC 2392,[1] Caldwell 39, PN G197.8+17.3
Central Star: HIP 36369, HD 59088, TYC 1372-1287-1

NGC 2392 lies about 6500 light-years away, and is visible with a small telescope in the constellation of Gemini.

Historic data
NGC 2392 in 32 inch telescope

The nebula was discovered by William Herschel on January 17, 1787, in Slough, England. He described it as "A star 9th magnitude with a pretty bright middle, nebulosity equally dispersed all around. A very remarkable phenomenon."[7] NGC 2392 WH IV-45 is included in the Astronomical League's Herschel 400 observing program.

Location

NGC 2392 is located just east of δ Geminorum, just south the ecliptic.

Naming controversy

On 11 August 2020, the IAU Working Group on Star Names (WGSN), NASA/IPAC Extragalactic Database (NED), and SIMBAD Astronomical Database (CDS) discontinued use of three nicknames that were perceived as offensive - "Eskimo Nebula", "Clown Face Nebula", and "Clownface Nebula" - and strongly recommended the nebula be referred to by its NGC designation in further publications.[8][1]

See also

Notes
    1. ^ Radius = distance × sin(angular size / 2) = ≥2900 ly * sin(48″ / 2) = ≥0.34 ly
    2. ^ 10.1 apparent magnitude - 5 * (log10(≥880 pc distance) - 1) = ≤0.4 absolute magnitude

    References
    1. "NGC 2392". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2006-12-22.
    2. Gaia Collaboration et al. (2018b): Summary of the contents and survey properties
    3. O'Dell, C. R.; Balick, B.; Hajian, A. R.; Henney, W. J.; et al. (2002). "Knots in Nearby Planetary Nebulae". The Astronomical Journal. 123 (6): 3329–3347. Bibcode:2002AJ....123.3329O. doi:10.1086/340726.
    4. Deep-Sky Companions: The Caldwell Objects, 2nd Edition, Stephen James O'Meara, 2016, p.181
    5. O'dell, C. R.; Balick, B.; Hajian, A. R.; Henney, W. J.; et al. (2003). "Knots in Planetary Nebulae". In S. J. Arthur & W. J. Henney (ed.). Revista Mexicana de Astronomía y Astrofísica (Serie de Conferencias). Winds, Bubbles, and Explosions: a conference to honor John Dyson, Pátzcuaro, Michoacán, México, September 9–13, 2002. 15. pp. 29–33. Bibcode:2003RMxAC..15...29O.
    6. Guerrero, M. A.; Chu, Y.-H.; Gruendl, R. A.; Meixner, M. (2005). "XMM-Newton detection of hot gas in the Eskimo Nebula: Shocked stellar wind or collimated outflows?". Astronomy and Astrophysics. 430 (3): L69–L72. arXiv:astro-ph/0412540. Bibcode:2005A&A...430L..69G. doi:10.1051/0004-6361:200400131.
    7. The Scientific Papers of Sir William Herschel by J. L. E. Dreyer, Royal Society, London 1912
    8. Talbert, Tricia (11 August 2020). "NASA to Reexamine Nicknames for Cosmic Objects". NASA. Retrieved 11 August 2020.

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