Meghnad Saha was an Indian astrophysicist who developed the Saha ionization equation, which is used to calculate the ionization state of atoms in stellar atmospheres. He also made significant contributions to the classification of galaxies.

The Hubble Sequence is a galaxy classification system developed by Edwin Hubble in the 1930s. It classifies galaxies into four main types: elliptical, spiral, barred spiral, and irregular.

Elliptical galaxies are characterized by a smooth, featureless appearance. They have a round or oval shape and do not have any spiral arms or bars.

Spiral galaxies are characterized by a flat disk with spiral arms. The spiral arms are made up of young stars, gas, and dust.

Barred spiral galaxies are characterized by a flat disk with a bar-shaped structure. The bar is made up of old stars and is typically surrounded by spiral arms.

Irregular galaxies are characterized by an irregular shape and no definite structure. They may contain young and old stars, gas, and dust.

Jayant Narlikar is an Indian astrophysicist who made significant contributions to the study of spiral galaxies. He developed a theory of spiral structure formation based on the idea of density waves.

The Kavalur Observatory is an Indian astronomical observatory located in Kavalur, Tamil Nadu. It is operated by the Indian Institute of Astrophysics and is known for its contributions to the study of galaxies.

T. Padmanabhan is an Indian astrophysicist who is known for his work on the evolution of galaxies. He has developed a theory of galaxy formation and evolution based on the idea of dark matter.

Astrosat is an Indian astronomical satellite launched in 2018. It is designed to study a wide range of astronomical objects, including galaxies, stars, and planets.

Virbhadra Singh Chauhan is an Indian astronomer who is known for his work on the classification of active galaxies. He has developed a classification system for active galaxies based on their spectral properties.

The Indian Astronomical Observatory is an Indian astronomical observatory located in Hanle, Ladakh. It is operated by the Indian Institute of Astrophysics and is known for its contributions to the study of galaxies.

Biman B. Nath is an Indian astronomer who is known for his work on the formation of galaxies. He has developed a theory of galaxy formation based on the idea of hierarchical clustering.

Astrosat-2 is an Indian astronomical satellite scheduled to be launched in 2022. It is designed to study a wide range of astronomical objects, including galaxies, stars, and planets.

Somnath Bharadwaj is an Indian astronomer who is known for his work on the structure of galaxies. He has developed a theory of galaxy structure based on the idea of dark matter halos.