Keats follows the thought-pattern of the Italian Petrarchan sonnet
division of the poem into octave and sestet is emphasized by a very prominent turn between the sections. Keats has chosen a sonnet as his preferred form here, but it seems a mix between a Petrarchan and Shakespearean.
Traditionally in the former, an idea is set out in the octave (the first eight lines) and is resolved in the sestet. Keats’ sonnet follows this pattern in that there is a clear volta (or tone change) in line nine.
"Bright star! would I were steadfast as thou art—"
Keats wishes he were as loyal and unwavering as the bright star. Maybe he wants to be as the North star; immobile — from the point of view of humans on the earth — and forever pointing in a clear direction.
The poet therefore desires to become more like the bright star, unchanging and utterly dependable. This line places him firmly in the Romantic genre, especially as he interprets his personal desire as a justification for how he wishes to live his life; in short, a free spirit. What he is becomes his own philosophy.
"Of snow upon the mountains and the moors"
The phrase ends with an image of the personified star ‘gazing’ on snow covered moors and mountains. Note the alliterative “m"s linking these words to reinforce their significance. This emphasises the desolation, as both are bleak and uninhabited.
The wintry imagery is apt for this poem, suggesting loneliness and harshness. Nature is uncompromising, as is the steadfast ideal that Keats seeks.
"Of pure ablution round earth's human shores, Or gazing on the new soft fallen mask"
Ablution means a ritual religious washing or cleansing - suggests a kind of holiness to the movement of the sea; it may also put us in mind of the biblical Great Flood, a sort of “ablution” of the human earth.
Keats refers back to what the star is “gazing” at. Here he uses enjambment to create a sense of suspense at the line break. This is cleverly done, because what follows is unexpected.
"No - yet still stedfast, still unchangable"
At the volta there is a firm ‘no’ followed by a second dash, another caesura. This line is important, on which the poem pivots. The repetition of ‘still’ gives further emphasis.
The ‘No’ is the point where a new direction is taken in the reasoning. The reference to the cosmos, the ‘steadfast’ and unchanging natural world is for the moment dismissed.
The poet doesn’t think he can be as steadfast as the star — and yet he is, in terms of his devotion to ‘my fair love’. It’s the moment where the star, is related to his own human life.
"Still, still to hear her tender-taken breath, And so live ever—or else swoon to death."
Regardless of the anxiety and stress associated with his love, it still gives him life and a reason to live. ‘tender-taken’ is a marvellous compound adjective, compressed, with gentle, alliterative ’t’s.
This poem was written towards the end of Keats' life, many saying that this was the last poem he composed.
The dash forms a caesura, creating a dramatic climax in the last line - elongated vowels in ‘swoon’ and ‘death’, stretching out the line, emphasising its significance.