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Popular Astronomy

July 2017

Just one contributor to the section this month! 

Mike Hezzlewood already submits drawings to both the SPA lunar and planetary sections.  He joined this section at the start of July and observed two planetary nebulae;  M27 the Dumbbell nebula in the constellation of Vulpecula and M57 the Ring nebula in Lyra.  Mike used a Takahashi FC 100 DC fluorite doublet refractor at x185 for M57 (below left) and x44 for M27 (below right).

Stars heavier than about 8 solar masses end their lives as supernovae; but theory tells us that smaller stars, down to about 0.8 solar masses will cast off their outer layers during the second giant phase (Asymptotic Giant Branch) leaving a "short lived" planetary nebula (lasting a few tens of thousands of years) and a white dwarf, the core remnant of the star.  It is the ultra violet radiation from the white dwarf which ionises the gases in the cast off layers, and when ions and electrons recombine photons are emitted at specific wavelengths giving the characteristic emission signatures of these objects.  

      

                                                                                                                                                                  Dave Finnigan

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