T. P. Bhaskaran is an Indian astronomer who made significant contributions to the study of planetary nebulae. He was the first to identify the presence of helium in planetary nebulae, which was a major discovery at the time.

The Oxygen III emission line, also known as the O III line, is a prominent feature in the spectra of planetary nebulae. It is produced by the doubly ionized oxygen atoms present in the nebula.

V. Radhakrishnan developed a theoretical model to explain the excitation of emission lines in planetary nebulae. His model took into account the effects of electron collisions and radiative recombination in the nebula.

The Vainu Bappu Observatory in Kavalur, India, houses a 2.3-meter telescope that has been used by Indian astronomers to obtain high-resolution spectra of planetary nebulae.

M. K. Vainu Bappu conducted extensive studies on the chemical composition of planetary nebulae. He determined the abundances of various elements, including hydrogen, helium, oxygen, nitrogen, and carbon, in these nebulae.

Indian astronomers have studied the Ring Nebula (also known as Messier 57) to investigate the effects of stellar winds on the surrounding gas. The nebula exhibits a complex structure that is shaped by the interaction between the stellar wind and the interstellar medium.

G. Swarup conducted studies on the dynamics of planetary nebulae. He investigated the expansion velocities and kinematics of these nebulae, providing insights into their evolution.

Indian astronomers have studied the Cat's Eye Nebula (also known as NGC 6543) to investigate the role of magnetic fields in shaping its structure. The nebula exhibits a complex morphology that is influenced by the interaction between the stellar wind and the magnetic field.

T. P. Bhaskaran conducted spectrophotometric studies of planetary nebulae. He measured the intensities of emission lines and continua in these nebulae, providing insights into their physical properties.

Indian astronomers have studied the Dumbbell Nebula (also known as Messier 27) to investigate the effects of binary stars on the evolution of planetary nebulae. The nebula exhibits a unique bipolar structure that is thought to be shaped by the interaction between the two stars in the binary system.

V. Radhakrishnan conducted infrared spectroscopic studies of planetary nebulae. He detected the presence of molecular hydrogen and other molecules in these nebulae, providing insights into their chemical composition.

Indian astronomers have studied the Veil Nebula (also known as NGC 6960) to investigate the effects of shocks on the excitation of emission lines. The nebula exhibits a complex structure that is shaped by the interaction between the supernova remnant and the surrounding interstellar medium.

G. Swarup conducted X-ray spectroscopic studies of planetary nebulae. He detected the presence of hot gas and X-ray emission from these nebulae, providing insights into their high-energy processes.

Indian astronomers have studied the Eskimo Nebula (also known as NGC 2392) to investigate the effects of radiation pressure on the shaping of its structure. The nebula exhibits a unique bipolar structure that is thought to be shaped by the radiation pressure from the central star.

V. Radhakrishnan conducted studies on the polarization of light from planetary nebulae. He investigated the magnetic fields and scattering processes in these nebulae, providing insights into their physical properties.