 What is the namesake of the feature found at 189.5w longitude?
CREATE TABLE table_21060 (
    "Name" text,
    "Latitude" text,
    "Longitude" text,
    "Diameter" text,
    "Year named" real,
    "Namesake" text
)
SELECT "Namesake" FROM table_21060 WHERE "Longitude" = '189.5W'