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", a book, published in 1609, that contains the results of the astronomer Johannes Kepler's ten-year-long investigation of the motion of what?