Planetary nebula classification
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Planetary nebulae are classified according to a scheme developed by Vorontsov-Velyaminov. This classification takes the shape of a Roman numeral, from I to VI, followed to a letter: Out of 200 billion stars, about 1500 planetary nebulae are exist in our galaxy are known to exist. I: Stellar image (like a star); II: Regular disc: III: Irregular disc: IV: Annular structure V: Irregular form between a planetary nebula and diffuse nebula; VI: Abnormal form without a regular structure (like an S or an 8, etc). Some more complex object shapes can be characterized by two classes, the second being written between brackets.
Other deep sky objects' classification: |