The satellites of Jupiter

Io: the volcanic moon of Jupiter

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.

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.

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”.

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.

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.

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.

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).

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.

On the 5th 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.

An amateur astronomer in Caserta sent us some photos because there the weather

was better.

Open Photo

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.

Thanks for your attention!

Work by:

Brignone Lorenzo, Gianti Alessandro, Rinaudo Anna, Viale Luca, Viara Francesco

Thanks to:

Paolo Demaria, Ascanio Trivisano