About the Book
Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Pages: 30. Chapters: Planetary nebula, Ring Nebula, Cat's Eye Nebula, NGC 6302, Helix Nebula, NGC 7027, Mz 3, Dumbbell Nebula, Planetary Nebula M2-9, List of planetary nebulae, Planetary nebula luminosity function, Abell 39, Little Dumbbell Nebula, Saturn Nebula, Stingray Nebula, Eskimo Nebula, NGC 2818, NGC 1514, Hourglass Nebula, Mz 1, Medusa Nebula, NGC 2440, Zanstra method, NGC 6826, NGC 7662, NGC 3242, NGC 3132, Owl Nebula, IC 4406, NGC 6751, Fast Low-Ionization Emission Region, NGC 2371-2, NGC 40, Red Spider Nebula, NGC 6072, IC 418, Soap bubble nebula, NGC 6741, NGC 2438, NGC 3195, NGC 6572, Little Ghost Nebula, NGC 3918, NGC 2867, NGC 246, Shapley 1, NGC 7008, NGC 2346, NGC 6818, Hen 2-47, NGC 5189, NGC 6210, NGC 2022, NGC 6578, NGC 6884, NGC 6790, NGC 5307, NGC 5315, NGC 6565, NGC 7354, Lemon slice nebula, NGC 5882, NGC 6781, M1-92, NGC 2899, NGC 1360, IC 289, NGC 7048, NGC 1535, IC 2448, IC 2149. Excerpt: A planetary nebula is an emission nebula consisting of an expanding glowing shell of ionized gas ejected during the asymptotic giant branch phase of certain types of stars late in their life. This name originated with their first discovery in the 18th century because of their similarity in appearance to giant planets when viewed through small optical telescopes, and is otherwise unrelated to the planets of the solar system. They are a relatively short-lived phenomenon, lasting a few tens of thousands of years, compared to a typical stellar lifetime of several billion years. At the end of the star's life, during the red giant phase, the outer layers of the star are expelled via pulsations and strong stellar winds. Without these opaque layers, the hot, luminous core emits ultraviolet radiation that ionizes the ejected outer layers of the star. This energized shell radiates as a planetary nebula. Planetary nebulae play a crucial...
