He adds, “Imagine a snowplow running down the highway and lifting the plow. It leaves behind a pile of snow.” “It’s that kind of idea that has left the cold classical music scene behind. That’s the core.”
In other words, Neptune dragged these objects with it as it migrated outward, but broke its gravitational hold on them when it “leaped out”, causing them to settle into the Kuiper Belt in the distinctive Neptune-sculpted kernel pattern that persists to this day.
Last year, Siraj and his advisors at Princeton began looking for other hidden structures in the Kuiper Belt with a new algorithm, analyzing 1,650 KB — about 10 times more objects than the 2011 study led by Jean-Robert Petit, which first identified the kernel.
The results consistently confirmed the presence of the original kernel, while also revealing a possible new “inner kernel” located at approximately 43 AU, although more research is needed to confirm this discovery, according to the team’s 2025 study.
“You have these two clumps, basically, at 43 and 44 AU,” explains Siraj. “It’s not clear whether they’re part of the same structure,” but “Either way, it’s probably another clue about Neptune’s migration, or some other process that created these clusters.”
As Rubin and other telescopes discover thousands more KBOs in the coming years, the nature and possible origins of these mysterious structures in the belt may become clearer, potentially opening new windows into the tumultuous origins of our Solar System.
In addition to reconstructing the early life of known planets, astronomers studying the Kuiper Belt are racing to look for unknown planets. The most famous example is the hypothetical giant world known as Planet Nine or Planet X, first proposed in 2016. Some scientists have suggested that the gravitational influence of this planet, if it exists, could explain the strangely clustered orbits within the Kuiper Belt, although this hypothetical world would be located several hundred AU beyond the belt.
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