Ghost of Jupiter (NGC 3242 / Caldwell 59)
Coordinates, Gaia DR3 distance (1.32 kpc), magnitude 7.7, Eye Nebula double-shell structure, and observing guide for NGC 3242 in Hydra.
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) | 7.7 mag | ± 0.1 mag | Integrated CCD aperture photometry | definitive | Revised New General Catalogue and Index Catalogue (RNGC/IC) |
| Heliocentric distance | 4305 ly | ± 160 ly | Gaia DR3 trigonometric parallax of 12.1-mag central star (1.32 ± 0.05 kpc) (J2016.0) | definitive | ESA Gaia Archive — Data Release 3 |
| Apparent outer disk diameter | 0.7 arcmin | ± 0.05 arcmin | Main oval disk (42″ × 36″; inner bright eye is 25″ × 16″) | definitive | Revised New General Catalogue and Index Catalogue (RNGC/IC) |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Ghost of Jupiter (NGC 3242 in Hydra) at RA 10h 24m 46.11s, Dec -18° 38′ 32.2″ within Hydra, 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
The Ghost of Jupiter (NGC 3242, Caldwell 59—also called the Eye Nebula) is a dazzling spring planetary nebula located 4,305 light-years (1.32 ± 0.05 kiloparsecs) away in central Hydra. Discovered by William Herschel on February 7, 1785, and observed by John Herschel from the Cape of Good Hope in 1830, the nebula earned its popular name because its 42 × 36 arcsecond oval disk matches the exact apparent angular diameter and slight polar flattening of the planet Jupiter.
Like the Saturn Nebula (NGC 7009) and Blinking Planetary (NGC 6826), NGC 3242 is a textbook triple-shell planetary nebula. Surrounding its 12.1-magnitude central star (HD 90255, surface temperature ~75,000 K) is a blazing 25 × 16 arcsecond inner elliptical rim—shaped like a human eye or lemon—enclosed within a softer 42-arcsecond middle shell and capped at the northwest and southeast vertices of the inner ellipse by two crimson low-ionization FLIER knots.
Deep narrowband and Spitzer infrared exposures also reveal a giant, 18-arcminute (~22-light-year) outer halo of ancient asymptotic giant branch mass-loss shells interacting with the interstellar medium as the nebula moves through the high Galactic disk.
Practical Visual Observing Guide
- Exceptionally easy to find just 1.8° directly south of the 3.8-magnitude orange star Mu Hydrae (μ Hya) in a sparse spring sky.
- Shining at visual magnitude 7.7 inside a 42-arcsecond disk, NGC 3242 is visible in 10×50 binoculars as a bluish 'star' and displays a vivid turquoise-blue color in any 70–120 mm telescope.
- At 180×–320× in a 150–250 mm aperture, the 12.1-magnitude central star ('pupil') sits inside the darker center of the bright 25″ × 16″ inner football ('iris'), surrounded by the paler 42″ outer oval.
Catalog Cross-Identifications & Aliases
Common Aliases: NGC 3242 · Ghost of Jupiter · Eye Nebula · Caldwell 59
| Catalog Authority | Identifier |
|---|---|
| NGC | NGC 3242 |
| SIMBAD | NGC 3242 |
| WIKIDATA | Q15838 |
Related Objects, Comparisons & Guides
Saturn Nebula (NGC 7009 in Aquarius)
Coordinates, Gaia DR3 distance (1.26 kpc), magnitude 8.0, low-ionization ansae jets, and high-power observing guide for NGC 7009 in Aquarius.
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.
Owl Nebula (Messier 97 / NGC 3587)
Coordinates, Gaia DR3 distance (805 pc), magnitude 9.9, Lord Rosse's twin dark eye cavities, and observing guide for the Owl Nebula in Ursa Major.
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