Planetary nebula classification

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:

  • a: a shinier core
  • b: Uniform brightness
  • c: Presence of an annular structure

    III: Irregular disc:

  • a: Irregular brightness
  • b: Presence of an annular structure;

    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.

    IC 4997 - Planetary nebula of class I

    IC 3568 - Nebula planetary of class II (IIa)

    M57 - Ring Nebula of class IV (III) located in the constellation Lyra

    NGC 2899 - Nebula planetary of class VI

    Other deep sky objects' classification:

  • Globular clusters
  • Open clusters
  • Galaxies