In 1610, Italian astronomer Galileo Galilei made an incredible discovery: he observed, using a homemade telescope, four points of light orbiting the planet Jupiter. He thought they were distant stars, but soon realized that they moved regularly and differently from other stars. They also remained close to Jupiter, but changed their positions relative to each other. Galileo concluded that it was not stars but moons that revolved around Jupiter, providing strong evidence for the Copernican theory that most celestial objects did not revolve around the Earth.

The four moons that Galileo discovered are today known as the Galilean moons, in his honor. They are Io, Europa, Ganymede and Callisto, and are Jupiter's largest and brightest moons. Each of them has unique characteristics, such as the volcanoes on Io, the icy surface of Europa, the magnetic field of Ganymede and the craters of Callisto. Scientists have a special interest in Europa, as there is the possibility that it has an underground ocean that could harbor life.

Galileo's discovery was an important milestone in the development of modern astronomy. He showed that the solar system was more complex and diverse than previously thought, and that there were other worlds to explore. He also challenged the dominant view of the time, based on the authority of the Church and tradition, and advocated the use of observation and reason to understand the universe. For this he faced persecution and censure, and was condemned for heresy. He remained under house arrest for the rest of his life, but continued to study and write about his ideas.

Galileo is considered one of the fathers of modern science, and his discovery of Jupiter's moons is an example of his curiosity, creativity and courage. He inspires us to look up to the sky with wonder and to seek knowledge with passion.