Friday, 25 May 2018

NGC3242: Jupiter's Ghost

Low on the horizon, for northern observers, during the early spring months... in an otherwise seemingly empty part of the sky you may stumble upon this big and bright planetary nebula. It's popular name "Jupiter's Ghost" refers to its similar apparent size and shape compared to the biggest planet of our solar system. In reality this nebula is some two light-years across and is still in full expansion. It merely appears the size of Jupiter because it is 1,400 light-years away.

The bright inner halo, the central star's dying breath, was blown into space some 1,500 years ago and is now rapidly catching up with the large outer shell which gradually built up during the final phase of the star's life. It's central star of 11th magnitude was not that easy to see, although it's radiating at over 150,000°C and lighting up the gas bubble around it. The gas is heated up to the extent that it begins to ionise and emit a bluish-green light of its own. Actually, we're catching this nebula right at its brightest phase. Within the next couple of thousand years it will expand further, fade and eventually dissolve into space.

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