What would objective goodness and badness be like?

What does it mean for some act to be really, objectively bad?  Or really, objectively good?  This is a question that has puzzled philosophers for thousands of years.  Some think that there can be no such objective nature of morality; others that there can be some sort of shared morality recognised by most mentally healthy humans, a sort of pretty-much-universal form of common experience that is a reasonable substitute for objectivity.  

But what would true objective morality actually be like?  Where could it reside external to the minds of humans and other sentient beings?   There is a problem with this, as moral standards are felt emotionally, they are connected with empathy, with conscience.   Also, a moral standard that wasn't in some way subjective would not need interpreting.  It would not be possible to think of a moral position related to that standard and have a subjective position on that standard, as then we are in the situation of subjectivity - if we are in a position to question whether or not something is really wrong, or really right, then we lose the objective aspect of that moral question.  

The problem, I suggest, is this - the only way an objective moral value can exist is if it's not possible to have a subjective alternative feeling about it.  Objective morality must mean unchallengeable consciences.   

Or does it?