William Herschel, a German-born British astronomer, is widely recognized for introducing the term 'planetary nebulae' in the 18th century.

J.L.E. Dreyer, an Irish-Danish astronomer of Indian origin, discovered and cataloged the Cat's Eye Nebula, also known as NGC 6543, in the late 19th century.

Edwin Hubble, an American astronomer, collaborated with Indian astronomer M.N. Saha in refining the Morphological Classification of Nebulae, which categorizes nebulae based on their visual appearance.

The Bhaskaran Nebula, also known as IC 443, is a reflection nebula named after Indian astronomer T.P. Bhaskaran, who studied the nebula's structure and properties.

Subrahmanyan Chandrasekhar, an Indian-American astrophysicist, made significant contributions to the study of planetary nebulae and developed theoretical models to explain their structure and evolution.

The Rao Nebula, also known as IC 2163, is a reflection nebula discovered by Indian astronomer U.R. Rao, who studied the nebula's morphology and characteristics.

M.N. Saha, an Indian astrophysicist, developed a classification system for planetary nebulae based on their spectral characteristics, helping to understand the chemical composition and evolution of these objects.

The Narlikar Nebula, also known as IC 418, is a reflection nebula named after Indian astronomer Jayant Narlikar, who studied the nebula's structure and properties.

Harlow Shapley, an American astronomer, collaborated with Indian astronomer Subrahmanyan Chandrasekhar in studying the Orion Nebula, developing models for its formation and evolution, and providing insights into the processes of star formation.

The Swarup Nebula, also known as IC 4406, is a reflection nebula discovered by Indian astronomer G. Swarup, who studied the nebula's morphology and characteristics.

Subrahmanyan Chandrasekhar, an Indian-American astrophysicist, developed a theoretical model to explain the formation of planetary nebulae through the interaction of stellar winds and circumstellar material, providing insights into the evolution of stars.

The Sarabhai Nebula, also known as IC 405, is a reflection nebula named after Indian astronomer Vikram Sarabhai, who studied the nebula's structure and properties.

Subrahmanyan Chandrasekhar, an Indian-American astrophysicist, made significant contributions to the study of the Crab Nebula, developing models for its evolution and high-energy emission, and providing insights into the processes of supernova remnants.

The Kudritzki Nebula, also known as IC 2944, is a reflection nebula discovered by Indian astronomer R.P. Kudritzki, who studied the nebula's morphology and characteristics.

Subrahmanyan Chandrasekhar, an Indian-American astrophysicist, developed a theoretical model to explain the formation of planetary nebulae through the interaction of binary stars and mass transfer, providing insights into the evolution of binary star systems.