Massive new galaxy turns out to be 99.99 percent dark matter

Powerful telescopes have revealed that a nearby galaxy is 99.99 percent dark matter. That number is a new record and the galaxy’s existence could help us learn more about the properties of dark matter, which makes up about 27 percent of the universe but hasn’t been officially detected.

The galaxy, called Dragonfly 44, is 300 million light years away. It has the same mass as our own Milky Way but has a hundred times fewer stars. The lack of stars means that the galaxy is dim enough to have been hidden for decades. It’s not the only galaxy to be composed of almost all dark matter, but most of the other ones are tiny dwarf galaxies, not ones a trillion times more massive than our Sun.

Astronomers at Hawaii’s WM Keck Observatory spotted...