Lighting the Nebulae

Mercury, July/August 2002 Table of Contents

Courtesy of the Hubble Heritage Team (AURA/STScI/NASA).

by James B. Kaler

The interplay of light and atoms paints the beautiful palette of planetary nebulae.

When I was about 13 years old, I pointed my terribly aberrated 3-inch telescope between Beta and Gamma Lyrae. To my amazement, I actually found the Ring Nebula (M57). Although I had seen pictures, the memory of that ghostly smoke ring still holds more fascination for me than the Hubble pictures do today. Shortly thereafter I located the next best of the backyard planetary nebulae, the Dumbbell (M27). No other planetaries seemed to be within my poor telescope’s reach, but no matter, my interest in these marvelous creations had begun.

Even as a teenager I knew that the nebulae were somehow illuminated by their central stars, but I was in college before I learned how that feat is actually accomplished. Textbooks often slough off the explanation by saying that the nebulae are lit by some kind of fluorescence, and let it go at that, as if serious physical descriptions are inherently uninteresting. Part of the joy of astronomy, however, is not simply seeing the sights, but in understanding why the sights are there in the first place. So come along on a trip to the inside of a planetary nebula and see what really happens as light and atoms violently interact to create some of the loveliest objects in the night sky.

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