How do dark nebulae reveal themselves against a bright background?
Answer
They are seen through silhouette, effectively blocking the visible light originating from objects situated directly behind them.
Dark nebulae represent regions where visibility is achieved not by emitted or reflected light, but by the complete absence or blockage of light from sources lying beyond them. These clouds possess such high density or contain such a large concentration of opaque dust that they function as cosmic screens. When positioned between an observer and a luminous background, such as the star-dense plane of the Milky Way, these clouds obscure the background light, revealing themselves purely through contrast as a dark silhouette or patch against the brighter expanse.
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