About 65 million light-years away, the galaxy called NGC1052-DF2 is dim and diffuse, coming in at about one two-hundredths the mass of our Milky Way. Normally, not all of a galaxy’s mass is visible.

Radio telescopes detect a large cloud of hydrogen gas (contour lines) where no stars can be found Neutral hydrogen gas streams between NGC 4254 (top left) and the dark galaxy VIRGOH121 (centre ...

If it were close enough to study, a galaxy that is almost totally dark might be quiet enough for scientists to pick out the first direct evidence of dark matter. Advertisement.