In the January 2026 issue of Planetary and Space Science (vol. 270):
Courtot, A. Shober, P. Vaubaillon, J. Orbit dissimilarity criteria in meteor showers: A comparative review Art 106231 .2025.106231
The dissimilarity criterion (“D” value) is how we group meteoroids and their resulting meteors, versus the background of sporadic, unrelated events. Do multiple meteor(oids) belong together, in a “meteor shower”? Or are two meteors just coincidentally similar? We do this more rigorously than just gauging by eye. And yet, it’s an open question, since that background level is no joke. Meanwhile, two meteors in space may truly come from the same parent comet/asteroid/comet-asteroid, yet drift apart into (slightly) different orbits. Courtot et al. attempt to bring more rigor.