Subrahmanyan Chandrasekhar, a renowned Indian-American astrophysicist, made significant contributions to the study of nebulae and the development of methods for estimating their masses.

Chandrasekhar's method relies on the Virial Theorem, which relates the total kinetic and potential energies of a system in equilibrium.

Chandrasekhar's formula relates the mass of a nebula to the velocity dispersion of its constituent gas and the size of the nebula.

Chandrasekhar's mass limit, also known as the Chandrasekhar limit, is the maximum mass a white dwarf can have before it collapses under its own gravity, leading to a supernova.

T. P. Prabhu, an Indian astronomer, conducted extensive research on the Orion Nebula, contributing to our understanding of its structure, dynamics, and star formation processes.

Prabhu's observations of the Orion Nebula revealed the presence of molecular clouds, which are dense regions of gas and dust where star formation occurs.

J. C. Bhattacharya, an Indian radio astronomer, made significant contributions to the development of radio astronomy techniques and their application in studying nebulae.

Bhattacharya's pioneering work led to the discovery of pulsar wind nebulae, which are regions of high-energy emission produced by the interaction of a pulsar's relativistic wind with the surrounding medium.

R. N. Iyengar, an Indian astronomer, conducted extensive research on the Large Magellanic Cloud (LMC) and its nebulae, contributing to our understanding of their structure, dynamics, and star formation processes.

Iyengar's observations of the LMC revealed the presence of supernova remnants, which are the expanding remnants of massive stars that have undergone a supernova explosion.

G. S. Vahia, an Indian astronomer, conducted extensive research on the Crab Nebula, contributing to our understanding of its structure, dynamics, and high-energy emission.

Vahia's observations of the Crab Nebula revealed the presence of a supernova remnant, which is the expanding remnant of a massive star that has undergone a supernova explosion.

S. Chandrasekhar, an Indian-American astrophysicist, made significant contributions to the development of theoretical models for the evolution of nebulae, including the theory of radiative transfer and the theory of stellar evolution.

Chandrasekhar's theoretical models provided insights into the formation and structure of nebulae, the dynamics of gas and dust in nebulae, the evolution of stars within nebulae, and the interaction between nebulae and their surroundings.

Albert Einstein, while a renowned physicist, was not an Indian astronomer who contributed to the study of nebulae mass measurements. The other options, Subrahmanyan Chandrasekhar, T. P. Prabhu, and J. C. Bhattacharya, are Indian astronomers who made significant contributions to this field.