Simplify the following text for a Grade 6 native English-speaking person.
Original: Otto Struve ( August 12 , 1897 , Kharkov , Russian Empire â `` April 6 , 1963 , Berkeley , USA ) was a Russianâ `` American astronomer of Baltic German ethnicity .
Simplified: Otto Struve ( August 12 1897 â `` April 6 1963 ) was a Russian astronomer .