Who is Ahab from Ahab's Wife, or, the Star-gazer: A Novel and what is their importance?

Ahab is a sea captain and the husband of Una. He is her second husband and is ive years older than she is. Ahab is in his fifties when he meets Una. He performs the ceremony for her marriage to Kit and brings them back to Nantucket. When Kit disappears, Ahab marries Una and they have a son Justice. On his second voyage, his leg is lost to the great white whale Moby Dick. He is obsessed with killing the whale and dies at sea in the effort.