 On September 28 , 2007 the main belt asteroid <unk> ( <unk> P @-@ L ) was named after him and is now known as <unk> <unk> . The asteroid was discovered October 17 , 1960 by Cornelis Johannes van Houten and Ingrid van Houten @-@ <unk> at Leiden Observatory , where they were studying photographic plates taken by Tom <unk> using the Palomar Observatory 's Samuel Oschin telescope . 
