这几句英语如何解释

这几句英语如何解释
(1)He is the younger og the two brothers
我想问的是这里younger前面为什么要加the 呢?
(2)Beyond the stars , the astronaut saw nothing but space
我想问的是stars前面为什么要加the,而space前面不加the.
(3)We elected him headmaster of our school for a second time.
我想问的是headmaster前面怎么不加定冠词,而second time后面要加定冠词a 呢?顺便问一下这句话是什么意思.
(4)That man doesn't look like his age; I think he's somewhat in his sixties.
除了用in his sixties 表示,还有其他表示在他60岁的短语吗?
(5)Most students can go to college for further education in our city.
(6)We should have confidence in ourselves and we will make it if we have a try.
后面2句是想知道它们的翻译.