LitCharts assigns a color and icon to each theme in The Sun is Also a Star, which you can use to track the themes throughout the work.
Immigration and the American Dream
Passion vs. Reason
Interconnectedness and Destiny
Isolation vs. Connection
Summary
Analysis
Natasha puts her personal items—phone, headphones, backpack—into a bin before she walks through the metal detector. She doesn't smile as the guard, Irene, checks Natasha's items. Irene flips over Natasha's phone case, which is the cover art for the Nirvana album Nevermind. That album has been Natasha's lifeline since the immigration debacle began; she finds comfort in hearing Kurt Cobain voice her pain. Natasha reasons that Irene probably hates her job, especially since Irene gives no indication that she recognizes Natasha.
Even as Natasha will go on to insist that passion is silly, her narration here suggests that she's passionate about 90s grunge music like Nirvana. This is, in part, because that music is often deals with loneliness, and it's comforting to know that there are other people out there experiencing similar sadness and pain. Although it’s clear that Natasha is lonely, it seems like she's isolating herself to deal with it, which will only exacerbate the problem.