Twilight last night was fantastically clear and the forecast was good so I set up my 80mm refractor. Took me quite a while since I hadn’t set up my deep sky kit since May.Was a bit slow to polar align and took quite a while to get Autoguider set up.
So, it was with some dismay I saw the clouds come in. I got one 2 minute sub of the open cluster M52 in Cassiopeia and beside it, the beautiful, fragile bubble nebula, Caldwell 11.
This is a bubble of space within a cloud of hydrogen gas. The bubble has been blown by the intense stellar wind coming off a Wolf-Rayet star in the centre. A Wolf-Rayet is a massive star that has blown off its envelope and consists just of a remnant naked stellar core.
WRs are so massive that they burn their nuclear fuel quickly to support their weight and have a short stellar lifespan. They end their lives as Type 1b or 1c Supernovae. They may also be responsible for some gamma ray bursts as there is no envelope to shield the radiation associated with a core collapse supernova.
A direct hit from a gamma ray burst would be, um, very bad for Earth!
The surrounding shell of hydrogen gas around this star is excited by the intense radiation of the stellar wind and glows bright red (hydrogen alpha band, 656nm).
I had planned to take about an hour of 5 min exposures, this is just 2 minutes with no dark or flat frames 😦
Look for the edge of the bubble in the red area near top right.