EI2GYB > ASTRO    22.11.25 10:30l 58 Lines 5439 Bytes #200 (0) @ WW
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Subj: distinct structure in Kuiper belt discovered
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Sent: 251122/1112Z 47819@EI2GYB.DGL.IRL.EURO LinBPQ6.0.25

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Potentially distinct structure in Kuiper belt discovered with help of clustering algorithm

A vast region of our solar system, called the Kuiper belt, stretches from the orbit of Neptune out to 50 or so astronomical units (AU), where an AU is the distance between Earth and the sun. This region consists mostly of icy objects and small rocky bodies, like Pluto. Scientists believe Kuiper belt objects (KPOs) are remnants left over from the formation of the solar system.

Now, a new preprint paper on arXiv describes a newly identified region that appears to be completely distinct from other parts of the Kuiper belt-but some uncertainty remains.
The kernel

Back in 2011, a team of astronomers noticed a denser region of the objects located within the Kuiper belt at around 44 AU. The team dubbed this region the "kernel" and found that the objects within it had low ecliptic inclinations and eccentricities compared to other KPOs.

In other words, their orbits were more circular and lay closer to the plane of the solar system, rather than at an angle. The kernel itself is within another distinct population of KPOs, referred to as the "dynamically cold" population, in which all objects tend to have lower eccentricities and inclinations.

Because the initial observation of the kernel was visual in nature, it might have lacked some of the finer details. Some researchers wondered whether a deeper dive into data on these objects might reveal new features within the kernel or other parts of the Kuiper belt.
Clustering algorithm raises new questions

To search for distinct structures within the Kuiper belt, the authors of the new preprint paper decided to try out a clustering algorithm, called Density-Based Spatial Clustering of Applications with Noise (DBSCAN). The algorithm had been used for other astronomical datasets, but not for the Kuiper belt. The team first calculated barycentric free orbital elements, like the semimajor axis, eccentricity and inclination for 1,650 classical KBOs and used DBSCAN on these to search for other clusters of similar objects.

Their algorithm found, not only the kernel, but also another distinct structure right next to it, at about 43 AU, which they simply refer to as the inner kernel. The inner kernel sticks out as potentially separate due to its eccentricity distribution being narrower than the kernel's, suggesting a distinct population. They say the inner kernel contains 7-10% of the classical KBOs.

However, the team says the distinction between the kernel and inner kernel depends on clustering parameters. This leaves some question about whether or not the inner kernel is really distinct.

"The discovery of the inner kernel, described here, was achieved by using DBSCAN in a conditional manner-requiring that DBSCAN recover the kernel, and asking whether in those cases it simultaneously identified any other cluster(s). However, removing this condition, it is unclear whether the inner kernel and the kernel are a single, combined structure, or actually two distinct ones," the team explains.
New data on the way

For the moment, the inner belt's existence as a separate entity is still unclear. However, new data from the Vera C. Rubin Observatory is coming soon and should provide more clarification. This, as well as other surveys, can clarify the nature of these structures and more about their origins.

To the study authors, however, the inner belt is still significant. They say, "There are two alternative explanations that we cannot distinguish between: either the kernel is significantly larger than previously thought, or there is an additional distinct structure in the cold classical Kuiper belt. In either case, the inner kernel, as described here, is the additional component."






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