Edwin Hubble developed the first comprehensive classification system for nebulae in 1926, based on their appearance and morphological characteristics.

Harinder Singh Ahluwalia conducted extensive research on planetary nebulae, contributing to the understanding of their structure, composition, and evolution.

Meghnad Saha developed the Saha Classification System for emission nebulae, which categorizes them based on their excitation mechanisms and spectral characteristics.

Subrahmanyan Chandrasekhar collaborated with Otto Struve in the development of the Yerkes Classification System for nebulae, which was based on their spectral characteristics.

The Hubble Sequence classifies galaxies based on their morphological appearance, such as elliptical, spiral, and irregular galaxies.

Govind Swarup conducted extensive research on the Magellanic Clouds, contributing to the understanding of their structure, composition, and star formation processes.

Jayant Narlikar developed the Narlikar Classification System for active galactic nuclei, which categorizes them based on their spectral properties and emission mechanisms.

Subrahmanyan Chandrasekhar collaborated with William Morgan and Philip Keenan in the development of the Morgan-Keenan Classification System for stars, which is based on their spectral characteristics.

The Yerkes Classification System classifies nebulae based on their spectral type, which indicates the presence of specific elements and ionization levels.

Vikram Sarabhai conducted extensive research on supernova remnants, contributing to the understanding of their structure, composition, and evolution.

Harinder Singh Ahluwalia developed the Ahluwalia Classification System for planetary nebulae, which categorizes them based on their morphological characteristics and ionization levels.

Jayant Narlikar collaborated with Gerard de Vaucouleurs in the development of the de Vaucouleurs Classification System for galaxies, which is based on their morphological characteristics and surface brightness profiles.

The Morgan-Keenan Classification System classifies stars based on their spectral type, which indicates the presence of specific elements and ionization levels.

Govind Swarup conducted extensive research on H II regions, contributing to the understanding of their structure, composition, and star formation processes.

Meghnad Saha developed the Saha Classification System for galaxies, which categorizes them based on their morphological characteristics and spectral properties.