Tuesday 30 May 2017

A strange turtle

Hercules is famous for its two magnificent globular clusters: M13 and M92. For the rest that part of the sky is fairly empty, apart from some interesting double stars such as Ras Algethi or a few very faint and distant galaxies. And yet... in this forgotten part of the sky lies this very interesting planetary nebula. NGC6210 or more popularly the "Turtle Nebula" may be tiny but, if sky conditions permit you to increase telescope power considerably, you'll notice that it's one of the planetaries that shows the most detail. Easily visible were the two "ansae", external gas lobes that are blown out of the main shell by strong winds that come from the central star's poles. Also the extremely complex internal structures were readily visible.

The Turtle is the dying breath of a star slightly smaller than our Sun, 6,500 lightyears away, and it currently undergoes its most active phase. Clearly it's much more evolved than the proto-planetary nebula I showed you yesterday. Astronomers are dazzled about this unusual little nebula because it shows many different layers and a strange, somewhat bent overall shape. Jets of hot gas are piercing through these layers, creating complex holes and pillars. In a few thousand years the inner layers will catch up with the faint outer shell that already escaped from the unstable star just before it collapsed and the nebula will dissipate into space. Our Sun awaits the same tragic fate in about five billion years...

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