Table schema:
CREATE TABLE table_name_72 (object_type VARCHAR, ngc_number VARCHAR, right_ascension___j2000__ VARCHAR)

Question: Name the object type with an NGC number more than 6638 and right ascensions being 18h25m37.8s
SQL: SELECT object_type FROM table_name_72 WHERE ngc_number > 6638 AND right_ascension___j2000__ = "18h25m37.8s"