PASADENA, Calif. - Between feedings and diaper changes of his newborn daughter, Michael E. Brown may yet find an 11th planet. Once conducted almost exclusively on cold, lonely nights, observational astronomy these days is often done under bright California sunshine. When he has a few spare minutes, Dr. Brown, a professor of planetary astronomy at the California Institute of Technology, downloads images taken during a previous night by a robotically driven telescope at Palomar Observatory 100 miles away. Each night, the telescope scans a different swath of sky, photographing each patch three times, spaced an hour and a half apart....