Simplify the following text for a Grade 10 native English-speaking person.
Original: It was discovered by Johann Palisa on February 25 , 1892 in Vienna , making it one of the last large ( diameter over 200 km ) asteroids discovered .
Simplified: It was found by Johann Palisa on February 25 , 1892 in Vienna , making it one of the last big ( diameter over 200 km ) asteroids found .