Figure 11-25 Planetary Nebulae (a) The pinkish blob is a planetary nebula surrounding a star in the globular cluster M15, about 33,000 ly from Earth in the constellation Pegasus. (b) The planetary nebula Abell 39 is about 7000 ly from Earth in the constellation Hercules. The almost perfectly spherical shell that constitutes the nebula is about 5 ly in diameter; the thickness of the shell is only about 0.3 ly. (c) This infrared image of the planetary nebula NGC 7027 suggests a more complex evolutionary history than that of Abell 39. NGC 7027 is about 900 pc (3000 ly) from Earth in the constellation Cygnus and is roughly 14,000 AU across.