M27 was discovered by Charles Messier on the 12th of July 1764. This was the first planetary nebula discovered by him. The name Dumbbell Nebula was given by John Herschel later when he took a better look at the shape of the nebula.
M27 is the second brightest planetary nebula in the sky, with a magnitude of 7.4. This nebula is next to M57 one of the most studied planetary nebulae.
The central star has a magnitude of 13.5 and has a surface temperature of about 85.000K. This star is part of a binary system, where the second star only has a magnitude of 17. The nebula has a complex structure of several shells. The central shell is about 1.2′ by 0.8′ and is a bit elongated. Perpendicular to this shell is the hourglas shaped shell of the nebula with a size of 4.5′ by 2.5′. This is all embedded in an elliptical shape of about 8.4′ by 6.1′.
In 1991 the first image was taken of the halo surrounding M27. In 1992 a scientific paper was published describing this outer shell…
http://www.astro-photo.nl/publication/discovery-paper-halo-m27/wppa_downloadThe surface brightness of this halo is about 1000x fainter than the central shell. When comparing the images in H-alpha and OIII clearly the different appearance of both gases can be seen. The H-alpha shows a lot of sub-structure, while the OIII is much more homogeneous.
The image
The image is the result of a collaberation between Terry Hancock, Fred Herrmann and André van der Hoeven. Images were taken with several setups and combined into one final image.
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