Is ‘Planet 9’ a second Kuiper Belt?

The Kuiper Belt is a massive collection of dwarf planet and asteroid-sized worlds orbiting far past Neptune. Is the hypothetical Planet 9 really a second such belt?

The announcement of a possible large ninth planet in our solar system way beyond Neptune last month caused a lot of excitement, needless to say. If confirmed, it may be similar to “super-Earth” type exoplanets which have been found to be plentiful around other stars, although none, that we knew of, around ours. At this point, however, it is still a well-presented theory. Now, there’s another possibility which has been offered to explain the weird orbits of some of the small Kuiper Belt objects – not a large planet, but rather a second Kuiper Belt consisting of many smaller objects instead. 

The new findings have been presented by researchers Ann-Marie Madigan and Michael McCourt at Harvard University, who suggest that Planet 9 may really be “a new Kuiper Belt that’s far more massive than the current-day Kuiper Belt, at larger distances, and preferentially lifted off the plane of the major planets,” as noted inNew Universe Daily. The theory will be published soon in the Monthly Notices of the Royal Astronomical Society. 

The hypothesis is similar to the ninth planet one in that it says that there must be more mass farther out in the Solar System to account for the odd orbits of some of the Kuiper Belt objects. But whether that mass is one larger planet or several, or more, smaller ones, isn't known yet. The new theory says that multiple smaller objects, like those found in the known Kuiper Belt, are more likely than one larger planet.