This also struck me as being pretty strange, but I think everything here can be weaseled around:

‘at the edge of the sector’: The Vulcan system happens to be at the edge of the sector it is contained within, sectors being vaguely defined chunks of space laid out fairly arbitrarily.

Surveying the moon: The ruins are well known and well explored (our heroes seem familiar with them already, for instance) but this weird energy vortex is new, strange, and merits a starship crew to investigate it. It’s not the first time they’ve sent Pike specifically to investigate a weird energy source popping up somewhere.