From spacetelescope.org:
An international team of researchers using the NASA/ESA Hubble Space Telescope and several other observatories have, for the first time, uncovered a galaxy in our cosmic neighbourhood that is missing most — if not all — of its dark matter. This discovery of the galaxy NGC 1052-DF2 challenges currently-accepted theories of and galaxy formation and provides new insights into the nature of dark matter. The results are published in Nature.
Dark matter is believed to be the one that holds galaxies together. This discovery requires us new knowledge on how galaxies work. It is exciting to know what’s the explanation behind this.