Adventure, exotic worlds and speculative technology: the space opera. Alien races and anomalous phenomena are common to the lore. The setting is usually the future but can just as easily be the past or present. There may be magic but such is typically tweaked and renamed. Regardless of its diverse particulars, the space opera is what it is and we recognize it immediately.
The fine line between science fiction and fantasy is the subjective notion of plausibility. The space opera is expected to be science fiction or fantasy in the guise thereof. Strange or advanced technology is a must. Should utter weirdness be the technology it must be explained “scientifically” even if such an explanation is sheer nonsense. The space opera must somehow be “futuristic” regardless of setting.
We are stirred by strangeness and thrilled by adventure. Like heroic fantasy, the space opera is all about being weird and adventurous. Realism and intensity make a story gritty and the space opera is no exception. Still, it is the unusual reality of the genre that gives it its distinct appeal.
The space opera is the epitome of all fiction. Science fiction, fantasy, adventure, horror, mystery, romance and war are all commonly associated with this one of every genre.