User blog comment:Tiredman2/Mass Effect Plot Holes and Contradictions/@comment-4953843-20120822075257/@comment-4953843-20120826191629

read all about it:. even 21st century humans such as ourselves can infer probable planetary compositions with comparatively primitive technology and techniques. and we are getting nearer and nearer by the day to detecting planets almost like earth. alien tech? obviously way more sophisticated.

now, aliens have had the whole galaxy to themselves for a long time. technology's bound to homogenize in most fields due to the regular interactions of the species and of course something as mundane as planetary mapping tech will be among those widely available to the citadel races. and, like most things mundane, easily overlooked and taken for granted. which, again, points to that certain alien mindset.

the term "galactic standard" isn't merely some fancy words.

and lastly, the Serpent Nebula is nowhere near the galactic core. it is, however, obscured by lots of gases (well it -is- a nebula). but as far as i can tell even primitive earth tech can and do study nebular compositions from time to time. all that sci-fi crap about instruments not detecting stuff a meter beyond some smoke is just plot convention - not just in mass effect.