Simplify the following text for a Grade 9 native English-speaking person.
Original: The International Year of Astronomy ( IYA2009 ) was a year-long celebration of astronomy that took place in 2009 to coincide with the 400th anniversary of the first recorded astronomical observations with a telescope by Galileo Galilei and the publication of Johannes Kepler 's Astronomia nova in the 17th century .
Simplified: The idea was to promote astronomy worldwide and get young people interested in it . The year 2009 , is special to astronomers as it is the 400th anniversary since the first astronomical telescope by Galileo Galilei was used .