Wednesday, 9 November 2016

One peanut for the price of two

When William Herschel discovered this planetary nebula back in 1785, he saw two separate lobes and believed them to be two separate objects that were so close that they seemed to run into one another. That's why a century or so later this nebula received two different ID numbers: NGC2371 and NGC2372. But today of course we know that it's just one single planetary that's arrived at the point where it starts breaking up. 

The thin shells of hot gas, remnants of the dying star's atmosphere, have been blown so far away - 1,3 lightyears to be precise - that they are splitting in two half spheres before disintegrating further. The central star has reached its maximum temperature of 118.000°C and will soon start to fade. Difficult to see through the telescope were the two "ansae", plumes of gas that  blew out of the star's polar regions where the atmosphere's less thick and that now form ethereal "clouds" at the astonishing distance of 3 lightyears from the central star (above and below on my sketch). Remember that the nearest star to Earth lies at a distance of 4,25 lightyears so you get a good idea of how far these ansae have wandered off from their origin. It's interesting to compare them to the ansae of the much younger and more active Saturn Nebula, which are clearly still plumes that are escaping from the polar chimneys. It's a bit like the smoke from a steam train that blows out in a puff and when the pressure's released leaves a dark cloud in the sky that quickly evaporates. In the case of our "Peanut Nebula", the clouds are almost gone. 

I absolutely had to share this object with you because it's an often neglected gem in the winter constellation of Gemini. With the nearby and famous Eskimo Nebula which attracts most of the spotlights, the little and somewhat obscure Peanut hardly receives any attention. Shame on us astronomers!  


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