The last four lines,its longer, more traditionally structured lines, affects a type of objectivity. From the objective standpoint, the star is nothing special, especially next to the planet Saturn. However, even in the midst of expressing himself objectively, the speaker takes a moment to insist he continues to pine for his star.
Then it stops like a bird; like a flower, hangs furled:
They must solace themselves with the Saturn above it.
What matter to me if their star is a world?
Mine has opened its soul to me; therefore I love it.