CREATE TABLE table_name_72 (object_type VARCHAR2, ngc_number VARCHAR2, right_ascension___j2000__ VARCHAR2)

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