Analysis: What's Up With the Title?
Properly speaking, Keats's poem doesn't have a title, which is why we refer to it by its first line. (Sometimes you'll see people referring to it simply as "Bright Star," which is a shortened version of the same idea.) Does this mean that Keats deliberately chose not to give it a title? Not necessarily. The fact is that the poem was only published in 1838, about seventeen years after Keats's death, so he didn't have final control about how it came down to us. Still, all things being equal, we still think that "Bright Star, would I were stedfast as thou art" is a pretty good title – because it gives a good idea about what the poem's about, but doesn't give anything away.
The best part about the title is what is most ambiguous about it. What's ambiguous here? Well, just from this line alone, it isn't clear what Keats means by "as." He could be saying to the star one of two things, either: (1) "would I were [as] stedfast as thou art," or (2) he could be saying "would I were stedfast [in the same way, looking down on Earth] as thou art." This ambiguity arises because the word "as" has multiple meanings. To find out what Keats means, we need more context – i.e., the rest of the poem.
As it turns out, Keats means "as" in the sense of option (1); he wants to be "AS stedfast AS" the star is (i.e., he wants to live forever without moving). But, interestingly enough, he spends the longest section of the poem, lines 2-8, describing in great detail why he really, completely, totally does not mean option (2), "would I were stedfast [in the same way, looking down on Earth] as thou art." To be stedfast in the same way as the star would mean hanging out in the loneliness of the eternal heavens, and the speaker doesn't want that. Thus, the first line is a great title for the poem because it provides a little bit of information and raises a lot of questions – questions that can only be answered by reading the poem.