Summary

All WISE featured images use colour to represent specific infrared wavelengths. Blue represents 3.4-micron light, cyan represents 4.6-micron light, green represents 12-micron light and red represents 22-micron light. In this image, we see a mixing of blue and cyan in the southern ridge that is not often seen in other WISE images. The north-eastern shell appears violet, indicating a mixture of longer infrared wavelengths from cooler dust (red) and shorter infrared wavelengths from luminescent gas (blue). About the Object: Names: Jellyfish Nebula (IC 443); Eta Geminorum (Propus) Type: Nebula > Supernova Remnant; Star > Variable. Distance: Approximately 1.5 kiloparsec or 4890 light years (IC 443). Size: Approximately 65 light years across (IC 443). Age: 5,000-10,000 years old (IC 443). Position of object (J2000): RA=06h 18m 02.7s; Dec=22° 39’ 36” (IC 443). RA=06h 14m 52.7s; Dec=22° 30’ 24.5” (Propus). Constellation: Gemini. Field of View: 1.56 x 1.56 degrees. Orientation: North is straight up. Colour Mapping: Blue=3.4 microns; Cyan=4.6 microns; Green=12 microns; Red=22 microns.

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Photo's description:

This oddly colourful nebula is the supernova remnant IC 443. IC 443 is the remains of a star that went supernova somewhere between 5,000 and 10,000 years ago. The blast from the supernova sent out shock waves that travelled through space, sweeping up and heating the surrounding gas and dust in the interstellar medium, and creating the supernova remnant seen in this image. What is unusual about the IC 443 is that its shell-like form has two halves that have different radii, structures and emissions. 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 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 north-eastern shell was probably created by a fast shock wave (100 kilometres per second), whereas the southern shell was probably created by a slow shock wave (30 kilometres per second).