"Spirograph Nebula"
"Raspberry Nebula"
"Red Planetary"

J2000
RA: 05h 27m 28.27s
Dec: -12 ° 41' 48.3"
Mag.10,70
Surface bright: 6,95
Dim.: 12"
Central star: 10,17 (var)
Constellation: Lepus

Discovery: Williamina Fleming, 1891
Distance: 0,609 kpc
Radius: 0,018 pc

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IC 418 is an important and very studied PN...but, strangely, less observed by skygazers. This nebula is very easy to find because of its high magnitude and higher superficial magnitude. Moreover, it's well recongnizeable also at low magnifications thanks to its angular dimension. With high magnifications it reveals a typical anular structure, slightly elliptical, looking like a walnut, with a bright central star.
The importance of this PN is due to its extreme youngness. The central star hasn't reached high temperatures yet, so that it cannot completely ionize expansion gases; that's why gases are looking thick. As a conseguence, the main emission is ionized hydrogen, and that's why it's red coloured in trichromy photos. Space Telescope's detailed images revealed a thin inner shell.
Most interesting for astronomers and amateurs, this nebula's central star is a variable: lots of measurements found out variation of brightness in few hours, but also in months! It also seems that short-period variations are irregular, long-period variations show regularity instead.
More studies could help to understand this oscillations.

Interesting level: ***