Triangulum II is a tiny little galaxy. It's only got 1,000 stars and it's not producing any new ones. It's probably dying.
But, for some reason, it has much more mass than it should. Scientists are hoping that's caused by a dark matter cluster. It could also be a bad measurement. Or, it might be that the galaxy is so tiny because it's too close to the Milky Way, which is stealing mass from it.
Who knows? And if there is a lot of dark matter in a galaxy that's mostly dead, is that a coincidence?