“Planetarium” is a free-verse, feminist poem inspired by Caroline Herschel and other astronomers. There is no regular meter—line lengths vary widely, from two-syllable (two-word) lines to 12-syllable lines. The stanzas also vary in length, from one line to 11 lines per stanza. There are 45 lines total, which take up most of two standard book-size pages. Most of the lines are left-aligned, but a few lines begin at different points across the page. According to the Princeton Encyclopedia of Poetry and Poetics, Rich’s feminist approach to poetry in the 1960s “required casting off the ‘asbestos gloves’ of traditional formalism” (482).

While Rich avoids traditional formal structures of poetry, she utilizes white space on both sides of the page. Stanzas 7 and 11 are both indented so that there is the blank white space of the page on both the right and the left of them. These two stanzas, which contain two lines each, are about Tycho Brahe, and set him visually apart from the previous left-aligned stanzas about Caroline Herschel. Rich indents Stanza 16 the same amount as Stanzas 7 and 11, but Stanza 16 contains only one line. This one-line stanza introduces the first-person “I” (Line 34) of the poem.