original question: how many Astronomical Discovery does [Galileo Galilei] have?
answer: 4
answer type: Astronomical Discovery.
auxiliary information: Galileo Galilei, was an Italian astronomer, physicist, engineer, philosopher, and mathematician who played a major role in the scientific revolution during the Renaissance. He is widely regarded as one of the greatest scientists of all time. His achievements include improvements to the telescope and consequent astronomical observations and support for heliocentrism. Galileo has been called the "father of modern observational astronomy", and the "father of modern physics", and "the father of modern science". His contributions to observational astronomy include the telescopic confirmation of the phases of Venus, the discovery of the four largest satellites of Jupiter, and the observation and analysis of sunspots. Galileo also worked in applied science and technology, inventing an improved military compass and other instruments. Galileo's championing of heliocentrism and Copernicanism was controversial within his lifetime, when most subscribed to either geocentrism or the Tychonic system. He met with opposition from astronomers, who doubted heliocentrism due to the absence of an observed stellar parallax.
What is the total amount of Astronomical discoveries that [Galileo Galilei] has?