Meghnad Saha, an eminent Indian astrophysicist, is often referred to as the 'Father of Indian Astronomy'. His groundbreaking work on stellar atmospheres and the theory of ionization equilibrium revolutionized our understanding of stellar physics.

Fred Hoyle, a prominent British astronomer with Indian roots, proposed the 'Steady-State Theory' in the 1940s. This theory suggested that the universe is continuously expanding and creating new matter, thus challenging the dominant 'Big Bang Theory' at the time.

Subrahmanyan Chandrasekhar, a Nobel laureate in Physics, made significant contributions to the study of black holes and stellar evolution. His work on the 'Chandrasekhar Limit' established a critical mass above which a star collapses under its own gravity, leading to the formation of a black hole.

Govind Swarup, a renowned Indian radio astronomer, discovered the first radio galaxy, Cygnus A, in 1953 using the Giant Metrewave Radio Telescope (GMRT). This discovery marked a significant milestone in the study of extragalactic radio sources and contributed to our understanding of the universe's large-scale structure.

Vikram Sarabhai, a visionary Indian scientist and space enthusiast, played a pivotal role in establishing the Indian Institute of Astrophysics (IIA) in Bengaluru. Founded in 1971, the IIA has become a prominent center for astronomical research in India, contributing to advancements in various fields of astrophysics.

S.N. Ghoshal, an eminent Indian physicist and cosmic ray researcher, made significant contributions to the study of cosmic rays. He discovered the 'Forbush Decrease' effect, which is a sudden decrease in the intensity of cosmic rays observed at Earth, caused by the interaction of solar storms with Earth's magnetic field.

James Jeans, a British mathematician and physicist, made significant contributions to the theory of stellar evolution and the study of galaxies. He proposed the concept of the 'Jeans Mass,' which is the critical mass required for a cloud of gas to collapse under its own gravity and form a star.

M.K. Vainu Bappu, a renowned Indian astronomer, played a crucial role in establishing the Vainu Bappu Observatory in Kavalur, Tamil Nadu. This observatory, named after him, has been a significant center for astronomical observations and research in India.

Albert Einstein, a German-born theoretical physicist, revolutionized our understanding of gravity and space-time with his theory of general relativity. His work laid the foundation for the study of black holes and opened up new avenues in the exploration of the universe.

M.N. Saha, an eminent Indian astrophysicist, made significant contributions to the study of stellar spectroscopy. He discovered the 'Ambartsumian-Saha Effect,' which relates the ionization state of a gas to its temperature and density, providing insights into the composition and structure of stars.

Arthur Eddington, a British astrophysicist, proposed the 'Eddington Luminosity Limit,' which establishes a theoretical upper limit on the luminosity of a star. This limit is determined by the balance between the outward radiation pressure and the inward gravitational force, providing insights into the stability and evolution of stars.

Homi J. Bhabha, a renowned Indian nuclear physicist, was instrumental in establishing the Tata Institute of Fundamental Research (TIFR) in Mumbai. TIFR has become a leading center for research in various fields of science, including astrophysics and cosmology, contributing significantly to India's scientific achievements.

Lord Kelvin, a British physicist and mathematician, proposed the 'Kelvin-Helmholtz Mechanism,' which explains how stars generate energy through the gravitational contraction and heating of their interiors. This mechanism played a crucial role in understanding the evolution and energy sources of stars.

A.K. Raychaudhuri, an eminent Indian astrophysicist, made significant contributions to the study of solar physics. He discovered the 'Raychaudhuri Effect,' which describes the expansion of the solar corona during solar flares, providing insights into the dynamics and behavior of the Sun's outer atmosphere.

Karl Schwarzschild, a German mathematician and physicist, derived the 'Schwarzschild Radius,' which defines the boundary of a black hole, beyond which nothing, not even light, can escape. His work laid the foundation for our understanding of black holes and their properties.