Sagitarrius A* is a super interesting object in the center of our galaxy, and we have solid evidence that it weighs a lot: it is "supermassive" (about 4 million times more massive than the Sun), and is super dense. So, we've been assuming that it is a supermassive black hole, as all observations we've made support this.

However, it could be something more exotic, like a wormhole. That would be awesome, but it's hard to tell the difference from 26,000 light years away(ish). However, researchers at Fudan University have shown the next-generation of telescopes we're building should be sensitive enough and have enough resolution to do exactly this. Science fiction, my friends, is hopefully about to become science fact.