1. The satellites of Jupiter Io: the volcanic moon of Jupiter

2. Galilean moons The Galilean moons are the four moons of Jupiter discovered by Galileo Galilei in January 1610. They are the largest of the many moons of Jupiter and derive their names from the lovers of Zeus: Io, Europa, Ganymede, and Callisto. They are among the most massive objects in the Solar System outside the Sun and the eight planets.

3. The four moons were discovered when Galileo made improvements to his telescope, which enabled him to observe celestial bodies more distinctly than had ever been possible before.

4. Galileo initially named his discovery the Cosmica Sidera ("Cosimo's stars“ to honor Cosimo De Medici, lord of Florence), but the names that eventually prevailed were chosen by Simon Marius. Galileo describes the moons of Jupiter in his most important astronomical treatise: the “Sidereus Nuncius”.

5. While watching the sky in January 1610 he noticed three little “stars” near Jupiter and he thought they belonged to the fixed stars. But in the following days he observed that they changed their position and he deduced that they revolved around Jupiter, so they were its satellites.

6. Our observations Since our school has an astronomical observatory we could repeat Galilean observation. Using the telescope we saw one of the satellites of Jupiter, Io.

7. Io Io is the innermost of the four Galilean moons of Jupiter and, with its diameter of 3,642 kilometers, the fourth-largest moon in the Solar System. It was named after Io, a priestess of Hera who became one of the lovers of Zeus.

8. Characteristics of Io Io orbits Jupiter at a distance of 421,700 km from the planet's center and 350,000 km from its cloudtops. It takes 42.5 hours to complete one orbit (fast enough for its motion to be observed over a single night of observation).

9. Like the other Galilean satellites of Jupiter and the Earth's Moon, Io rotates synchronously with its orbital period, keeping one face clearly pointed towards Jupiter. Io's colours derive from sulphur and molten silicate rock. Its unusual surface is kept very young by its system of more than 100 active volcanoes, the biggest one is called Pele.

10. On the 5 th April 2013, Io passed in front of Jupiter and we could observe it. Unfortunately at the beginning of the observation the sky was cloudy so we couldn’t see clearly the transit of Io.

11. An amateur astronomer in Caserta sent us some photos because there the weather was better. Open Photo

12. Around 10.30 p.m. the sky cleared up and so we could take some video of Jupiter and Io. Then using a software named Registax which processes the frames to the best possible picture we obtained these photos.

18. Thanks for your attention! Work by: Brignone Lorenzo, Gianti Alessandro, Rinaudo Anna, Viale Luca, Viara Francesco Thanks to: Paolo Demaria, Ascanio Trivisano