This is the 3388th most frequent Korean word.
달을
"달을" means "the moon" (as the object of a sentence).
In this sentence, '달을' uses the accusative particle '을' to mark '달' (moon) as the direct object of the verb '바라보다' (to look at).
달을 바라보며 소원을 빌었어요.
I looked at the moon and made a wish.
Here, '달을' refers to '작년 달' (last month), using '을' to denote it as the direct object being compared.
작년 달을 이길 수 있는 선수는 없었어요.
There was no athlete who could surpass last month's athlete.
In this context, '달을' indicates the moon depicted in the picture as the object observed, marked by '을'.