Eskimo / Clownface Nebula (NGC 2392 / Caldwell 39)
Coordinates, Gaia DR3 distance (1.76 kpc), magnitude 9.1, radial cometary filaments, X-ray binary core, and observing guide for NGC 2392 in Gemini.
Provenance-Backed Scientific Measurements
Every measurement below preserves its unit, uncertainty interval, observational method, reference epoch, quality status, and primary catalog source. See Uncertainty & Provenance for how competing measurements are handled.
| Parameter | Value | Uncertainty | Method & Epoch | Quality Status | Source Archive |
|---|---|---|---|---|---|
| Integrated visual magnitude (V) | 9.1 mag | ± 0.1 mag | Integrated CCD aperture photometry | definitive | Revised New General Catalogue and Index Catalogue (RNGC/IC) |
| Heliocentric distance | 5740 ly | ± 230 ly | Gaia DR3 trigonometric parallax of 10.5-mag central star (1.76 ± 0.07 kpc) (J2016.0) | definitive | ESA Gaia Archive — Data Release 3 |
| Apparent outer collar diameter | 0.8 arcmin | ± 0.05 arcmin | Outer parka hood ring (48″ × 44″; bright inner face is 18″) | definitive | Revised New General Catalogue and Index Catalogue (RNGC/IC) |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Eskimo Nebula (NGC 2392 / Clownface Nebula) at RA 07h 29m 10.77s, Dec +20° 54′ 42.5″ within Gemini, alongside peak meridian transit altitudes for 40°N and 30°S observers. Use the RA/Dec Coordinate Converter to compute exact culmination altitude for your latitude.
Astrophysical Context & Structure
NGC 2392 (Caldwell 39, traditionally known as the Eskimo, Clownface, or Lion Nebula) is a bright, multi-shell planetary nebula located 5,740 light-years (1.76 ± 0.07 kiloparsecs) away in central Gemini. Discovered by William Herschel on January 17, 1787, NGC 2392 became the first astronomical object imaged by the Hubble Space Telescope in December 1999 after its Servicing Mission 3A gyro replacement, revealing a tangled inner 'face' of two overlapping polar bubbles surrounded by a ring of orange-brown radially pointing 'cometary' knots.
Three-dimensional kinematic models show that we are viewing NGC 2392 nearly down the polar axis (~20° inclination) of a bipolar outflow: the inner 18-arcsecond 'face' consists of two prolate lobes expanding toward and away from Earth at up to 190 km/s, while the outer 48-arcsecond 'parka hood' or 'lion's mane' is an equatorial disk pierced by radial streamers sculpted as a fast stellar wind sweeps past dense AGB gas knots.
Chandra X-ray Observatory imaging revealed that NGC 2392's inner cavity contains abnormally hot diffuse X-ray plasma alongside hard X-ray emission from the 10.5-magnitude O6f central star (HD 59088)—strong evidence that the central star has an unseen, hot white-dwarf binary companion driving relativistic bipolar jets.
Practical Visual Observing Guide
- Located 2.4° southeast of Wasat (δ Geminorum) and just 40′ south-southeast of 5th-magnitude 63 Geminorum; a convenient 8.3-magnitude field star (HD 59087) sits just 95 arcseconds directly north of the nebula, creating a 'double star' effect in low-power finders where the southern star is fuzzy.
- In an 80–120 mm telescope at 100×–150×, the bright 10.5-magnitude central star ('the clown's nose') shines prominently inside a pale bluish-green disk.
- In a 200–350 mm aperture at 220×–350×, the dark moat separating the inner 18″ bubble from the mottled outer 48″ collar resolves into a detailed double ring.
Catalog Cross-Identifications & Aliases
Common Aliases: NGC 2392 · Eskimo Nebula · Clownface Nebula · Lion Nebula · Caldwell 39
| Catalog Authority | Identifier |
|---|---|
| NGC | NGC 2392 |
| SIMBAD | NGC 2392 |
| WIKIDATA | Q15843 |
Related Objects, Comparisons & Guides
Blinking Planetary (NGC 6826 in Cygnus)
Coordinates, Gaia DR3 distance (1.30 kpc), magnitude 8.8, rod/cone averted-vision blinking illusion, and observing guide for NGC 6826 in Cygnus.
Blue Snowball Nebula (NGC 7662 in Andromeda)
Coordinates, Gaia DR3 distance (1.76 kpc), magnitude 8.3, vivid O-III/He-II blue-green excitation, and observing guide for NGC 7662 in Andromeda.
Cat's Eye Nebula (NGC 6543 in Draco)
Coordinates, Gaia DR3 distance (1.07 kpc), William Huggins 1864 nebulium spectroscopy, and high-power observing guide for NGC 6543 in Draco.
Surface Brightness & Extended Objects Guide
Why surface brightness (mag/arcsec²) governs nebula and galaxy visibility more than integrated magnitude, and how exit pupil controls eyepiece contrast.
Angular Size, Separation & Field of View
How angular diameter (degrees, arcminutes, arcseconds), spherical angular separation, and small-angle physical diameter relate to telescope field of view.
Scientific Sources & Dataset Provenance
- ESA Gaia Archive — Data Release 3 (DR3 (2022-06-13)): Gaia Collaboration, Vallenari, A., et al. 2023, A&A, 674, A1 (Gaia Data Release 3) — European Space Agency / Gaia DPAC
- Revised New General Catalogue and Index Catalogue (RNGC/IC) (2024/2026 edition): Steinicke, W. 2010, Observing and Cataloguing Nebulae and Star Clusters (Cambridge Univ. Press); Verga, M. OpenNGC (CC-BY-SA 4.0 / data tables) — Wolfgang Steinicke / OpenNGC
- SIMBAD Astronomical Database (CDS) (2026-10 release): Wenger, M., et al. 2000, A&AS, 143, 9 (The SIMBAD astronomical database) — Centre de Données astronomiques de Strasbourg