An international network of observations for the International Year of Astronomy

International audienceThe equinox of Jupiter, defined as when the Sun passes through the plane of the equator of Jupiter and hence through the orbital plane of the Galilean satellites, will take place in 2009. The French committee for IYA20091 will take this opportunity to propose coordinated observations. The equinox of Jupiter is favourable for many events such as eclipses of the Galilean satellites by the planet Jupiter, occultations and transits and also mutual phenomena among the satellites themselves. These events are very easily observable, even with a small telescope, since the Galilean satellites are very bright. The events are spectacular since the satellites will disappear within a few seconds. We propose that these phenomena be observed worldwide by amateur astronomers, students and schoolchildren. Observers should send their data to a central website which will analyse each observation and provide a database of all the observations. Many observations can be explained in terms of the physics and the dynamics of the Galilean satellites themselves. The history of astronomy is also relevant as the Galilean satellites were the first celestial objects observed extensively from Earth and were used as the first reliable clock for longitude calculations. At the end of the observational campaign, the results will be collated and the scientific benefits from these observations will be explained and published