DdDm 1 - Planetary Nebula
The planetary nebula “DdDm 1” is located at a distance of 34,000 light-years in the halo of our Milky Way and can be found in the constellation
Hercules. The nebula can be best observed in the spring and summer months.
The shell of the PN consists of two components: an inner ellipse with an angular extent of 0.35x0.5“, and an outer ellipse of 0.95x1.1”,
corresponding to a true extent of 0.2 light-years. These two structures are surrounded by a much larger halo (1.75” and 0.3 light-years respectively).
The temperature of the nebula itself was determined to be 12,000 Kelvin, while the density is 4,000 particles per cm³.
The central star has an effective temperature of 55,000 Kelvin and shines 1,000 times brighter than our sun due to its high temperature. It is a
helium-burning star and originally had a mass of less than one solar mass.
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In my 20” Dobsonian, ‘DdDm 1’ appears quite bright and can be seen without any problems even at a low magnification of 120x due to its apparent
brightness of m= 14.7mag. Even at a much higher magnification of 380x, the PN appears absolutely point-like. There is no difference to the surrounding
stars. It shines completely colorless in a pure white tone.
