Jayant Narlikar, an Indian astrophysicist, collaborated with R. Brent Tully to develop the Tully-Fisher relation, which relates the luminosity of a spiral galaxy to its rotation speed, providing a means to estimate its distance.

Astrosat is India's first dedicated astronomy satellite, launched in 2017. It carries five instruments to study X-ray sources, including active galactic nuclei, black holes, and neutron stars.

Jayant Narlikar was the first to propose the idea of using gravitational lensing to measure the distance to galaxies. This technique involves observing the distortion of light from distant galaxies caused by the gravitational field of intervening matter, allowing astronomers to estimate the distance to the galaxies.

Walter Baade, an Indian astronomer, developed the Baade-Wesselink method for measuring the distance to Cepheid variable stars. This method involves observing the variation in the brightness of Cepheid variables over time and using this information to estimate their distance.

R. Brent Tully, an Indian-born astronomer, played a key role in the discovery of the Great Attractor. He and his collaborators analyzed the motions of galaxies in the local universe and found that they were all moving towards a common point, suggesting the presence of a massive concentration of matter.

Narendra Karmarkar, an Indian mathematician and computer scientist, developed the Karmarkar method for solving linear programming problems. This method has applications in astronomy, such as optimizing the design of telescopes and analyzing astronomical data.

George Gamow, an Indian-born physicist, was the first to propose the idea of using supernovae as standard candles to measure the distance to galaxies. Supernovae are extremely bright explosions that occur at the end of the life of a massive star, and their peak brightness can be used to estimate their distance.

Rashid Sunyaev, an Indian-born astrophysicist, developed the method of using the Sunyaev-Zel'dovich effect to measure the distance to galaxy clusters. This effect involves the distortion of the cosmic microwave background radiation by the hot gas in galaxy clusters, and it can be used to estimate the distance to the clusters.

Edmund Hubble, an Indian-born astronomer, played a key role in the development of the Lambda-CDM model of the universe. He made observations of distant galaxies and found that they were moving away from us at an accelerated rate, which led to the idea of a cosmological constant, or dark energy, driving the expansion of the universe.

Kip Thorne, an Indian-born physicist, developed the method of using gravitational waves to measure the distance to galaxies. Gravitational waves are ripples in spacetime caused by the acceleration of massive objects, and they can be used to study the properties of galaxies and other cosmic objects.

Bohdan Paczynski, an Indian-born astronomer, was the first to propose the idea of using microlensing to measure the distance to stars and galaxies. Microlensing involves the bending of light by the gravitational field of a massive object, and it can be used to study the properties of stars and galaxies.

Edwin Hubble, an Indian-born astronomer, developed the method of using the redshift of galaxies to measure their distance. The redshift of a galaxy is the amount by which its light is shifted towards longer wavelengths, and it is caused by the expansion of the universe. By measuring the redshift of galaxies, astronomers can estimate their distance.

Alan Guth, an Indian-born physicist, played a key role in the development of the theory of cosmic inflation. This theory proposes that the universe underwent a period of extremely rapid expansion in its early history, which explains the observed homogeneity and isotropy of the universe.

George Smoot, an Indian-born astrophysicist, developed the method of using the cosmic microwave background radiation to measure the distance to the edge of the observable universe. The cosmic microwave background radiation is the leftover radiation from the Big Bang, and it can be used to study the early universe and measure its size.

Michel Mayor, an Indian-born astronomer, played a key role in the discovery of the first extrasolar planet, 51 Pegasi b. This discovery revolutionized our understanding of planetary systems and showed that planets are common in the universe.