Astronomers have discovered what they believe is the first dark galaxy, a galaxy made almost entirely of dark matter. The galaxy, called Dragonfly 44, is located about 300 million light-years from Earth. It is about the same size as the Milky Way, but contains only about 1% as many stars.

The discovery of Dragonfly 44 is significant because it provides evidence for the existence of dark matter, a mysterious substance that makes up about 27% of the universe. Dark matter is invisible and does not interact with light, so it is very difficult to detect.

Astronomers believe that Dragonfly 44 is made almost entirely of dark matter because it contains very few stars. The galaxy is also very diffuse, meaning that its matter is spread out over a large volume. This makes it even harder to detect.

The discovery of Dragonfly 44 was made using the Hubble Space Telescope. Astronomers used the telescope to measure the galaxy's velocity and mass. They found that the galaxy's velocity was much higher than expected, given its mass. This suggests that the galaxy must contain a large amount of dark matter.

The discovery of Dragonfly 44 is an important step in our understanding of dark matter. It provides evidence for the existence of this mysterious substance and helps us to better understand the universe.