Sónar celebrates its 25th anniversary by sending a message in search of extraterrestrial intelligence. 33 musicians send music to GJ273b, a potentially habitable exoplanet, 12.4 light years from Earth. A celebration, an artistic and scientific experiment and a collective rumination on what it means to be human, and alien. In this film we interview Ignasi Ribas, astronomer and scientific partner of the project.