In 1609, as Galileo pointed the sky with a telescope, he observed Jupiter's satellites and changed our vision of the universe. Four hundred years later, we celebrate this event all over the world, and also in the Canaries. 2009, the International Year of Astronomy, is a very special year for the Science and Cosmos Museum (Museo de la Ciencia y el Cosmos). This was the first museum in Spain supported by a public entity, The Local Government of Tenerife (Cabildo de Tenerife), through its Autonomous Council of Museums (Organismo Autónomo de Museos y Centros), and a research centre, the Instituto de Astrofísica de Canarias. Fifteen years later, this museum, which receives 50,000 visitors a year, celebrates the International Year of Astronomy with fifty projects described in this paper.