https://www.vice.com/en_us/article/5dgpkk/scientists-discover-unexplained-barrier-at-our-galaxys-center

The center of our galaxy is an enigmatic place; shrouded in dust, we can't see it in visible light, and numerous mysteries abound, from novel radio signals emanating from unknown sources to weird gamma glows.

Now, a new study has added another mystery to the pile: scientists from the Chinese Academy of Sciences have detected the presence of an unexplained barrier blocking cosmic rays at the Milky Way's center. What's more, they don't really know what it is, according to an open access paper published in Nature Communications on Tuesday.