What is the defining visual characteristic of a Dark Nebula?
Answer
Dark patches or silhouettes against a brighter background.
Dark Nebulae are defined by their opacity; they are dense concentrations of gas and dust that are so thick they effectively block visible light emanating from sources situated behind them, whether those sources are distant stars or glowing nebulae. Consequently, they manifest visually as dark voids or silhouettes etched against a luminous backdrop. The Horsehead Nebula serves as a classic illustration of this principle, clearly demonstrating how a foreground dust cloud obscures the light from the emission source positioned immediately behind it.
#Videos
Nebulae: Crash Course Astronomy #36 - YouTube
Types of Nebulae - Clouds of Gas and Dust - YouTube
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