 The planet orbits at approximately 5 % of the distance between the Sun and Earth every four days . The star was observed several times between 2006 and 2009 , at first through the SuperWASP program and later through focused follow @-@ up observations . Analysis of collected radial velocity measurements led to the discovery of WASP @-@ 13b , which was reported in a journal on April 7 , 2009 . A follow @-@ up study published in 2011 investigated the cause for inflated planets such as WASP @-@ 13b , and re @-@ examined ( and re @-@ constrained ) its mass , radius , density , and age . 
