Astrophotography: The Dumbbell Nebula

Nebulae often signify the important events of a star's life. Where large diffuse nebulae typically form the materials needed for starbirth, planetary nebulae and supernova remnants signify the death of stars. Whether a dying star becomes a supernova or a planetary nebula depends on its mass: high mass stars, with large amounts of matter, can collapse gravitationally at the end of their lives, overcoming degenerate pressures and creating a sudden runaway nuclear reaction. Low and medium mass stars, with insufficient mass to collapse under its own weight, will slowly expel its outer layers in a slow and gradual death, forming a planetary nebula. One such example of a star that is undergoing this process is the dumbbell nebula. As the star puffs out its outer layers, the atmosphere of the star begins to disperse, creating a gas cloud that surrounds what used to be the core of the star - a white dwarf. Although nearing the end of their lives, white dwarf stars still emit high amounts of high energy radiation, primarily in the ultraviolet range. This ultraviolet radiation is capable of ionising the surrounding gas cloud, resulting in the emission of light as the ions recombine with electrons to form electrically neutral atoms. The recombination process produces a very exact wavelength of light, dependent on the nature of the ion, and the orbitals in which the electron transit involves. Since planetary nebulae are formed at the end of a star's life, large amounts of the higher elements tend to be present in the expanding nebular cloud. One such example is oxygen, which can produce greenish-blue light during ion-electron recombination. This is why the dumbbell nebula glows so strongly in the blue-green part of the spectrum.  

Photographic Information:

Imaging location: Changi, Singapore (Light pollution: Red zone/Outer City)

Date of data acquisition: 29 June 2014

Exposure Details: ~20min, 800mm FL at f/4

Camera: Canon EOS 600D Unmodified

Stacked with DSS, adjustment of curves and colors in Adobe Photoshop CS6.