Those who worried Hilary Duff's music career was "So Yesterday" needn't worry any longer! The pop star announced her musical comeback Wednesday after signing a contract with RCA Records. Her new single, "Chasing the Sun," was written by Colbie Caillat, Jason Reeves and Toby Gad. It will be available for digital download on July 29, the same day the music video is scheduled to debut on VEVO.