What term describes galaxies with clear, persistent, two-armed spiral structures?
Answer
Grand design spirals
Galaxies display considerable morphological diversity based on the underlying dynamics that govern their spiral features. Those galaxies exhibiting two strikingly clear, grand, and persistent spiral arms are specifically classified as 'grand design spirals.' This classification implies that these galaxies likely maintain a strong, coherent global density wave, perhaps initiated or sustained by a central feature like a strong star bar or sustained through robust interaction mechanisms. This contrasts sharply with 'flocculent spirals,' which feature many small, disconnected, and patchy arm segments, suggesting localized regeneration mechanisms rather than a single overarching global wave structure.
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