Eino never thought about other planets, he didn't even know there were other planets. He had never studied astronomy outside of Hogwarts and when he did he rarely paid attention so in contrast he did not raise his name. Not because he didn't think there really wasn't any life out there, he just hadn't the slightest clue about anything in relation to astronomy. The only way in which he studied the stars was as a form of divination, not scientifically, or however else it could be studied.