A Wolf-Rayet Star

NGC 6888 The crescent Nebula in the Constellation Cygnus - Autonomous Robotic Telescope - PIRATE Telescope - telescope.org - Open University - 1x3minute exposure -Sulphur, Hydrogen Alpha and Oxygen filters.

" A very disappointing 2017 Perseid Meteor shower here at the Jodrell  Plank Observatory in Lowestoft. The whole team turned out for two nights and early mornings but only managed to spot eleven meteors in total. We took over 600 x 15 second exposures at ISO 3200 using our automated Canon Cameras but failed to secure one image of a 2017 Perseid.  Hopefully, the LVST will have registered and recorded a  plethora of radar reflections from Perseid plasma trails in the upper atmosphere over the South of France. 

At about 2.30 am. on the 13th of August, just as we were about to pack up the equipment, our neighbour Mr Shrodinger, came around  saying that all our noise and comings and goings had spooked his cat. He neither knew where it was or whether it was dead or alive!  The poor man was in a right old quantum state". 

Kurt Thrust current Director of the Jodrell Plank Observatory.

Enlargement of the above widefield image of The Crescent Nebula with annotation identifying the Wolf-Rayet star HD192163 or WR136
- PIRATE Telescope - telescope.org - Open University

The Crescent Nebula is located not far from the star Sadr in the constellation Cygnus the Swan. The Nebula is being driven by the Wolf-Rayet Star HD192163 or WR136. Only stars some 30 times the mass of our Sun become Wolf-Rayet stars towards the end of their time on the main sequence and after they have gone through the 'red giant' phase of expansion.

Starmap showing the location of the Crescent Nebula - Credit SkyMap Pro and Pip Stakkert

'The Crescent Nebula (also known as NGC 6888, Caldwell 27, Sharpless 105) is an emission nebula in the constellation Cygnus, about 5000 light-years away from Earth. It was discovered by Friedrich Wilhelm Herschel in 1792. It is formed by the fast stellar wind from the Wolf-Rayet star WR 136 (HD 192163) colliding with and energizing the slower moving wind ejected by the star when it became a red giant around 250,000 to 400,000 years ago. The result of the collision is a shell and two shock waves, one moving outward and one moving inward. The inward moving shock wave heats the stellar wind to X-ray-emitting temperatures'. Credit Wikipedia

"The Wolf-Rayet star HD192163 is very very hot - having a surface temperature of 70,000 degrees K, in comparison the surface temperature of the Sun is a  mere 5,778 degrees K.  It is estimated that the star is 250,000 times brighter than the Sun. Its hot surface is emitting high energy ultra violet light which is causing the previously shed shells of gas to glow. There is evidence that the star is binary, having a low mass spectral class M or K companion star which revolves around a common centre of gravity every 5 days or so.  " Archie Mendes - visiting Astrophysicist and Mathematician.

For information regarding the spectrum of HD192163 follow the link:
 http://adsabs.harvard.edu/full/1975A%26A....40..459C