My annual effort to produce a satisfactory image of the 'Owl' nebula continues. This was done on a rather misty night last week but after what we've had this winter, have to take what I can get.

The 'Owl', despite being a Messier object, I always find rather difficult to image. It is faint for a Planetary and through the eyepiece not a lot to be seen in truth. But it is an interesting and unusual planetary and deserves some effort to produce a decent result.

When stars between a half and 4 times the mass of the Sun run out of their hydrogen fuel, they move on to burning helium into heavier elements, and continue to do so until the core temperatures and densities are unable to produce any further nuclear fusion.

And when that happens the swollen, giant star dies in a gentle-but-spectacular fashion.

The outer layers of the star are blown off over thousands of years, forming a planetary nebula. The remains of the star contract down to form a very hot, dense and small object known as a white dwarf.

Whilst some Planetaries are spherical in shape, about 80% of them eject a large amount of their matter in two jets in opposing directions and take on a more axisymmetric shape.

In the case of the Owl Nebula, these two jets are almost aligned with our line-of-sight, but are slightly off, and it’s the dust in those jets that blocks a sufficient amount of light from the expanding shell to cause the dark “eyes” to have their observed appearance.

You may notice that one of the eyes is “darker” than the other. That is because the “darker” eye is from the side of the nebula where the jet is emitted towards us, while the “fainter” eye is where the jet is emitted away from us.

This nebula is about three light years across and is around 6,000 years old. The star it came from was originally about twice the mass of our Sun, and the white dwarf at the center is now about the size of the Earth, 70% the mass of the Sun and at a surface temperature of around 100,000 Kelvin. (Or a temperature nearly 20 times that of our own Sun!)

My image consists of 45 x 120 sec exposures, sigma combined in AstroArt and further processed in PixInsight.

Credit to http://scienceblogs.com/startswithabang/2013/01/28/messier-monday-the-owl-nebula-m97/ for much of the information.

Many thanks,

David.