IC 443, also known as the Jellyfish Nebula, is a galactic supernova remnant (SNR) in the constellation Gemini. On the plan of the sky, it is located near the star Eta Geminorum. Its distance is roughly 5,000 light years from Earth, and is one of the best-studied cases of supernova remnants interacting with surrounding molecular clouds. IC 443 is known to harbour a neutron star, the remnant of the collapsed stellar core. The nebula has a physical size of roughly 300 light years across.
Normally faint and elusive, the Jellyfish Nebula is caught in this alluring telescopic mosaic. The scene is anchored right and left by two bright stars, Mu and Eta Geminorum, at the foot of the celestial twin (Gemini) while the Jellyfish Nebula is the brighter arcing ridge of emission with dangling tentacles below and right of center.
The SNR optical and radio morphology is shell-like, consisting of two connected sub-shells with different centers and radii. IC 443 shows very similar features to the class of mixed morphology SNRs. In this false-color infrared image, blue marks expanding gas where emission is dominated by excited iron atoms; the southern ridge (in red) is dominated by molecular hydrogen emission. In this and other images here, north is up, east is left.
X-ray and the optical images are characterized by a dark lane, crossing IC 443 from northwest to southeast. The larger north-eastern shell, seen here as the violet-coloured semi-circle on the top left of the supernova remnant, is composed of sheet-like filaments that are emitting light from iron, neon, silicon and oxygen gas atoms and dust particles heated by the blast from the supernova. The forward shock has encountered a wall of neutral hydrogen, and is propagating into a less dense medium with a much higher velocity at 80–100 km sec, than in the southern ridge. The smaller southern shell, seen here in a bright cyan colour on the bottom half of the image, is constructed of denser clumps and knots primarily emitting light from hydrogen gas and heated dust. These clumps are part of a molecular cloud which can be seen in this image as the greenish cloud cutting across IC 443 from the north-west to south-east. The colour differences seen in this image represent different wavelengths of infrared emission. The differences in colour are also the result of differences in the energies of the shock waves hitting the interstellar medium. The blast wave has been strongly decelerated by the cloud and is moving with an estimated velocity of roughly 30–40 km sec. In the western region, the shock wave breaks out into a more homogeneous and rarefied medium.
Credits: NASA, Wikipedia.