This is very cool, I'm anxious to see the full announcement and see what is said. I want to hear what others in the field see and have to say as well because I would never think a body with a diameter of just 250 km could actually have enough gravitational power to maintain rings.
How much mass you need to retain rings isn't an absolute quantity. It depends on distance and size of other masses. A 250km body in Earth orbit couldn't retain its own rings because Earth's gravity would dominate the system. But a 250km body in deep space with no competition could.
Neptune can actually maintain satellites at a greater distance than Jupiter can, despite Jupiter having over 10x the mass. This is because Jupiter has closer competition from the Sun and Saturn, while Neptune has enormous amounts of space to itself.
