Aryabhata (476-550 CE) is widely regarded as the father of Indian astronomy. He made significant contributions to mathematics, astronomy, and physics, including the development of the heliocentric model of the solar system.

Bhaskara II (1114-1185 CE) proposed the theory of gravitation in his work, the Siddhanta Shiromani. He described the force of attraction between objects and its dependence on their mass.

Brahmagupta (598-668 CE) discovered the concept of zero and its use in mathematics and astronomy. He developed the Brahmagupta's identity, which is a formula for calculating the area of a cyclic quadrilateral.

Varahamihira (505-587 CE) developed the first accurate trigonometric tables, which were used for astronomical calculations and predictions.

Aryabhata proposed the idea of a spherical Earth and its rotation on its axis. He also calculated the Earth's circumference with remarkable accuracy.

Bhaskara II developed the theory of planetary motion and elliptical orbits. He also calculated the sidereal periods of the planets and the Moon.

Varahamihira discovered the precession of the equinoxes and calculated its period. He also developed a system for predicting eclipses.

Varahamihira developed the concept of the zodiac and the twelve signs. He also wrote extensively about astrology and its applications.

Aryabhata discovered the existence of comets and their orbital characteristics. He also developed a method for calculating the trajectory of comets.

Varahamihira developed the theory of planetary conjunctions and their effects. He also wrote extensively about the influence of planets on human affairs.

Bhaskara II discovered the existence of sunspots and their impact on solar activity. He also developed a method for predicting solar eclipses.

Aryabhata developed the theory of lunar phases and their relationship to the Earth's shadow. He also calculated the size and distance of the Moon.

Varahamihira discovered the existence of nebulae and their classification. He also wrote extensively about the nature and properties of stars.

Bhaskara II developed the theory of stellar evolution and the life cycle of stars. He also calculated the masses and densities of stars.

The discovery of black holes is a relatively recent development in astrophysics and was not made by any of the astronomers mentioned in the options.