IC 418 - Planetary Nebula
IC 418 is a bright planetary nebula in the constellation Lepus with a brightness of 9.3mag and a size of 14x10" (arcseconds). It was discovered in March
1891 by Wilhelmina Fleming. The distance is given as 3,300 light-years, but values of 4,100 light-years can also be found.
The complex shell structure of the PN is still not understood today. The spirograph pattern (which gave the PN its name) is attributed to chaotic stellar
winds from the central star. Essentially, the nebula consists of an elliptical ring 0.22 light-years (or 2.1 trillion kilometers) in diameter, expanding into
space at a velocity of 27.4km/s. The ring is surrounded by several ionized shells, which have a temperature of up to 10,000 Kelvin. The total mass of the
nebula is about 0.15 solar masses.
The central star with the designation "ZZ Lep" belongs to the class of "variable stars" and can increase its brightness within hours. With a surface temperature
of up to 46,000 Kelvin it belongs to spectral class O7 and therefore emits most of its radiation in UV. It has a mass of 2.8 solar masses and is 1.8
times larger than our sun. The luminosity of this hot star is an incredible 7,700 suns. The enormous stellar winds rush outwards with a speed of up to 480 km/s
and carry away 3.8x10-8 solar masses every year. Thereby the environment is heated up to 3 million Kelvin.
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IC 418 is very bright in my 20" f/3 telescope and cannot be missed. The color is a bit peculiar - not greenish like other PN, but rather whitish-yellow.
The inner area is also very bright and in the center you can see the bright central star. In the outer areas a delicate ring structure is indicated. Unfortunately
there is no spirograph pattern visible, the envelope does also not appear mottled. A few brighter stars can be seen in the field of view.
A pretty nice object!
