Isolation is a very important theme in "Bright Star" because it is the deal-breaker. How so? Well, in the first line, the speaker says he wants to be like a star. But then, in the second line, he changes course. What makes him change his mind? The star's isolation "in lone splendor hung aloft the night." The description of the star's isolation then only gets worse and worse, until it culminates in a chill-inducing image of cold, blank, barren snow landing on the cold, blank, barren mountains and moors. It's only in the second section of the poem – beginning in line 9 – that the speaker clarifies what he even likes about the star. He likes the fact that it exists forever, and he wishes that he could too – but only if he can do it with his head resting forever on his girlfriend's breast. He wants connection for all eternity: an eternity of isolation just isn't worth it.
The most isolated figure in the poem is the speaker. Even though the star and the waters are isolated, they aren't the ones complaining about it in sonnet-form.
The poem does not give any indication that the speaker believes in an afterlife. Thus, if he thinks of death as simple non-existence, it would provide an escape from isolation.