Who is the Italian astronomer known for using a telescope to study the stars?

The Italian astronomer known for using a telescope to study the stars is Galileo Galilei. He made significant contributions to the field of astronomy, particularly through his improvements to the telescope and his meticulous observations of celestial bodies. Galileo's use of the telescope allowed him to discover moons around Jupiter, observe the phases of Venus, and study sunspots, greatly enhancing the understanding of the universe during his time. His work provided substantial evidence in support of the heliocentric model of the solar system, thereby challenging long-standing geocentric views.

Other astronomers mentioned, such as Copernicus, Newton, and Kepler, made important contributions to the field, but they did not utilize the telescope for their discoveries as Galileo did. Copernicus is known for proposing the heliocentric theory before telescopes were invented, Newton is famous for his laws of motion and gravity, and Kepler is known for formulating the laws of planetary motion based on observations made by Tycho Brahe. Thus, Galileo's pioneering use of the telescope places him distinctly in the context of astronomical advancements in the early 17th century.