The Footprint, the Egg, and the Butterfly.

The nebula is probably not an emission nebula, but a reflexion nebula which obscures the peculiar star by which it is illuminated." OBSERVING Before producing the beautiful glowing shells of planetary nebulae, low- to intermediate-mass stars (0.8 to 8 solar masses) eventually exhaust their core fuel supply of hydrogen and helium. One Tiny Footprint In 1946, German-American Germa astronomer mer Rudolph Minkowski began a survey of planetary nebulae using objective-prism survey plates at Mount Wilson Observatory. The nebula lies in a dense Milky Way field, but an orange 10th-magnitude star just 30" to the west highlights the spot. [Extracted from the article]