Simplify the following text for a Grade 12 native English-speaking person.
Original: George Adamski ( April 17 , 1891 â `` April 23 , 1965 ) was a Polish-born American citizen who became widely known in ufology circles , and to some degree in popular culture , after he claimed to have photographed ships from other planets , met with friendly Nordic alien `` Space Brothers '' , and to have taken flights with them .
Simplified: George Adamski ( April 17 , 1891 â `` April 23 , 1965 ) was a Polish-born American who became known in ufology circles after he said he photographed ships from other planets , met with aliens , and took flights with them .