This is the 1592nd most frequent Russian word.
становятся
"Become" or "turn into."
The word 'становятся' here is used to describe the process of becoming closer - a transition or change in state.
Друзья становятся ближе, когда они проводят больше времени вместе.
Friends become closer when they spend more time together.
In this case, 'становятся' is used to express the change in the length of days, indicating a seasonal progression.
Дни становятся длиннее весной.
The days get longer in spring.
Here, 'становятся' demonstrates a person's attainment of fame, illustrative of a transformative process.