Trans-Neptunian objects (TNOs) are icy bodies with diameters ranging from 1,500 miles to tens of miles. Their orbits are diverse but reflect the outward migration of Uranus and Neptune early in solar system history. The James Webb Space Telescope has provided unprecedented information about TNOs, shedding light on their composition and origin.
The telescope’s Near Infrared Spectrograph (NIRSpec) instrument has revealed distinct spectral classes among TNOs, including Bowl-type, Double-dip, and Cliff spectra. These classifications are based on the spectral shape in the 2.5-4 micron region and indicate different surface compositions. The DiSCo-TNOs program, led by John Stansberry and Bryan Holler, has identified three distinct types of TNOs, each with unique features.
The team hypothesizes that the differences in spectral types are due to variations in temperature, with Bowl-type objects forming closer to the Sun and Double-dip and Cliff objects forming farther out. This hypothesis is supported by the fact that all undisturbed cold-classical orbits have Cliff spectra.
Future observations will continue to explore TNOs, including their satellites and binary systems. The James Webb Space Telescope has already provided high-quality spectra of over 75 TNOs, offering a comprehensive look at these icy bodies in our solar system.
Source: https://blogs.nasa.gov/webb/2025/02/12/nasas-webb-reveals-the-ancient-surfaces-of-trans-neptunian-objects