“Picture a snowplow moving down a highway and lifting its blade. It leaves a lump of snow in its wake,” he adds. “That very idea is what left the cluster of cold classicals behind. That is the kernel.”
Put another way, Neptune hauled those objects outward with it, then broke its gravitational grip when it “jumped,” leaving them to settle into the Kuiper Belt in the distinctive, Neptune-sculpted kernel pattern that endures today.
Last year, Siraj and his advisers at Princeton set out to hunt for other hidden patterns in the Kuiper Belt using a new algorithm that examined 1,650 KBOs—about ten times the number of objects analyzed in the 2011 study led by Jean-Robert Petit that first identified the kernel.
The results repeatedly confirmed the original kernel’s presence while also hinting at a potential new “inner kernel” around 43 AU, though more study is required to verify this, according to the team’s 2025 study.
“There are essentially two clumps at 43 and 44 AU,” Siraj explains. “It’s not clear whether they’re part of the same structure,” but “in any case, it’s another clue about, perhaps, Neptune’s migration, or some other process that produced these clumps.”
As Rubin and other telescopes discover thousands more KBOs in the years ahead, the character and possible origin of these mysterious structures in the belt may come into sharper focus, potentially opening new windows onto the turbulent origins of our solar system.
Beyond reconstructing the early histories of the known planets, astronomers studying the Kuiper Belt are also racing to detect unknown worlds. The most famous candidate is the hypothetical giant known as Planet Nine or Planet X, proposed in 2016. Some researchers have suggested that this planet’s gravitational pull, if it exists, could explain oddly clustered orbits in the Kuiper Belt, though such a speculative world would lie well beyond the belt, at a distance of several hundred AU.
