Cometary belt around distant multi-planet system hints at hidden or wandering planets

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) radio observatory in Chile have made the first high-resolution image of the belt of comets (a region analogous to the Kuiper belt in our own Solar System, where Pluto and may smaller objects are found) around HR 8799, the only star where multiple planets have been imaged directly. The shape of this dusty disk, particularly its inner edge, is surprisingly inconsistent with the orbits of the planets, suggesting that either t