Supernova Remnants · Constellation Gemini

Jellyfish Nebula (IC 443 / Sharpless 2-248)

Coordinates, Gaia DR3 distance (1.72 kpc), CXOU J061705.3+222127 pulsar wind nebula, and observing guide for IC 443 in Gemini.

Right Ascension (J2000.0)06h 17m 00.00s
Declination (J2000.0)+22° 34′ 00.0″
Primary ClassificationMixed-morphology core-collapse supernova remnant
Best Observing SeasonWinter (December–March)

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.

Astrometric, Photometric, and Physical Parameters for Jellyfish Nebula (IC 443 / Sharpless 2-248)
ParameterValueUncertaintyMethod & EpochQuality StatusSource Archive
Integrated visual magnitude (V)12 mag± 0.5 magIntegrated optical filament photometrymodel-dependentRevised New General Catalogue and Index Catalogue (RNGC/IC)
Heliocentric distance5610 ly± 260 lyGaia DR3 3D dust extinction jump & Gem OB1 parallax (1.72 ± 0.08 kpc) (J2016.0)definitiveESA Gaia Archive — Data Release 3
Apparent diameter50 arcmin± 4 arcminOptical and radio blast shell (50′ × 40′)definitiveRevised New General Catalogue and Index Catalogue (RNGC/IC)
Measurement Uncertainties & Competing Solutions: Because IC 443's blast wave propagates into two media of vastly different density (a dense molecular cloud in the south vs. an atomic H I shell in the northeast), kinematic age estimates span 3,000 to 30,000 years despite a well-pinned 1.72 ± 0.08 kpc Gaia distance.

J2000 Equatorial Sky Chart & Culmination Altitude

The chart below plots Jellyfish Nebula (IC 443 Supernova Remnant) at RA 06h 17m 00.00s, Dec +22° 34′ 00.0″ 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.

J2000 Equatorial Sky Position (Gemini) +90° 0° −90° 24h 12h RA 0h Peak Meridian Altitude 73° 40°N Lat 37° 30°S Lat RA: 06h 17m 00.00s Dec: +22° 34′ 00.0″ Epoch: J2000.0 · V = 12 mag First-party vector diagram derived from IAU / CDS SIMBAD / Gaia DR3 astrometry.

Astrophysical Context & Structure

The Jellyfish Nebula (IC 443, Sharpless 2-248, SNR G189.1+03.0) is the textbook example of a 'mixed-morphology' core-collapse supernova remnant interacting with a giant molecular cloud, located 5,610 light-years (1.72 ± 0.08 kiloparsecs) away near the western foot of Gemini. Discovered photographically by Max Wolf on September 25, 1892, IC 443 spans 50 × 40 arcminutes (~75 light-years physically) and displays a bright, dome-shaped northeastern shell trailing curved southwestern filaments that resemble the tentacles of a swimming jellyfish.

Why are the two halves of IC 443 so asymmetric? In the northeast, the supernova blast wave is expanding at ~100 km/s into a lower-density atomic hydrogen cavity, lighting up crisp optical filaments of H-alpha, [S II], and [O III]. In the south and southwest, the shock has slammed head-on at ~30 km/s into a dense molecular cloud containing ~10,000 solar masses of gas, exciting 1720 MHz hydroxyl (OH) masers and accelerating cosmic-ray protons that collide with ambient gas nuclei to produce pion-decay GeV and TeV gamma rays observed by Fermi-LAT and VERITAS.

Inside the southern rim, Chandra X-ray Observatory pinpointed the compact remnant of the exploded massive star: CXOU J061705.3+222127, a hot magnetized neutron star hurtling southward at ~250 km/s and trailing a swept-back cometary pulsar wind nebula.

Practical Visual Observing Guide

Minimum Instrument150–200 mm telescope + O-III or UHC filter under dark skies
Recommended Magnification30×–65× wide-field with O-III or UHC filter
Best Evening SeasonWinter (December–March)
  • Located just 45 arcminutes east-northeast of 3.3-magnitude Eta Geminorum (Propus), along the line toward Mu Geminorum (Tejat) and 2° southeast of open cluster M35.
  • Visually, only the brightest 25′ × 5′ northeastern sickle-shaped rim has enough [O III] and H-beta surface brightness to be spotted; dark skies (Bortle 1–3), a wide-field 150–300 mm+ telescope at 35×–65×, and an O-III or UHC filter are required.
  • Sweep Eta Geminorum just outside the southwestern field stop to eliminate glare, and trace the curved northeastern cap where it threads between 8th- and 9th-magnitude field stars.

Catalog Cross-Identifications & Aliases

Common Aliases: IC 443 · Jellyfish Nebula · Sharpless 2-248 · SNR G189.1+03.0

Cross-Catalog Identifiers for Jellyfish Nebula (IC 443 / Sharpless 2-248)
Catalog AuthorityIdentifier
ICIC 443
SIMBADIC 443
WIKIDATAQ1078671
Related Object · Gemini

Messier 35 (NGC 2168 & NGC 2158 Pair)

Coordinates, Gaia DR3 distance (889 pc), magnitude 5.1, background cluster NGC 2158 contrast, and observing guide for M35 in Gemini.

Related Object · Taurus

Spaghetti Nebula (Simeis 147 in Taurus)

Coordinates, pulsar VLBI distance (1.30 kpc), 3-degree filamentary shell, runaway pulsar PSR J0538+2817, and guide for Simeis 147 in Taurus.

Reference Guide

Bortle Dark-Sky Scale & Sky Brightness Guide

Reference guide to the 9-class Bortle Dark-Sky Scale, zenith Sky Quality Meter (SQM) readings in mag/arcsec², naked-eye limiting magnitude, and light pollution.

Scientific Sources & Dataset Provenance

  • 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
  • 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
  • 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