Sunday, 4 June 2017

Racquetballs are blue

In the same part of the sky where you can find the Turtle Nebula, you may bump into this little bugger. At low power you might mistake it for an unusually blue star because it's so tiny, but pushing magnifications will reveal a surprising amount of detail. It's still a very young planetary nebula, not more than a few thousand years old, slightly more evolved than the Footprint Nebula. If the ancient Egyptians had a telescope, they would only have seen a reddish little star. Compared to the Footprint, the Blue Racquetball's central star has completely shed its atmosphere and the exposed, extremely hot core has started to heat up the surrounding gas shells up to the point that they're emitting light. You can clearly see the faint, external shell of gas that had already been expelled earlier during the last and very unstable phase of the star's life. The very complex inner structures consist of the star's atmosphere that's now whirling ever further into space, blown away by the powerful winds that the star's collapse generated. The best guess for this nebula's distance is 4,900 lightyears which would mean that the nebula's a third of a lightyear across. This is still fairly small and that's why we see it so brightly. Within another couple of thousand years, the gas cloud will have grown over a lightyear across and the dispersed gas will dim, eventually becoming invisible.   

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