Sunday 2 September 2018

NGC6803: More complex than one might think

Not even a degree from NGC6804 resides another planetary nebula. NGC6803 appears much smaller than its neighbour, but this is only because it lies much further away from us (10,000 light-years). This means that amateur telescopes will not reveal much more than an almost stellar-like object. Even with my binoscope at 507x, details were difficult to make out, although I did see its very hot central star (surface temperature 90,000°C!) surrounded by a bright, elliptical shell with two opposite lobes.

This bright shell is of particular interest because it contains much more elements such as carbon, oxygen and neon than most other planetary nebulae. These unusual abundances suggest that its central star was born in a metal-rich zone in the later stage of galactic evolution. Possibly the nebula's progenitor star could have been a star similar to our Sun but part of a close binary system. The matter exchange between both components, rich in heavier elements as byproducts of nuclear fusion, contributed to the abundances we now observe in the nebula. Comparison with data from 1995 shows that the shell has become much denser over this (astronomically) very brief period and indicates the existence of very complex structures. Obviously much more research needs to be done.

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