Simplify the following text for a Grade 12 native English-speaking person.
Original: Recently , comets Shoemaker-Levy 9 , Schwassmann-Wachmann-3 ( 73\/P ) , C\/1999 S4 LINEAR , and 57\/P du Toit-Neujmin-Delporte , have been seen to disintegrate .
Simplified: More recently , comets Schwassmann-Wachmann-3 ( 73\/P ) , C\/1999 S4 LINEAR , and 57\/P du Toit-Neujmin-Delporte , have been observed to disintegrate during their passage close to the Sun .