Astronomers combining observations from the Hubble Space Telescope and James Webb Space Telescope have discovered 27 new trans-Neptunian objects orbiting beyond Neptune, measuring as small as 5 kilometers across, BBC Sky at Night Magazine reported.
Preserving Solar System Origins Beyond Neptune
Some of the smallest objects in the outer Solar System appear to have preserved clues to how they formed billions of years ago. This persistence occurred despite expectations that collisions should have altered them over astronomical timescales.
Researchers studied these newly discovered trans-Neptunian objects using high-powered space telescopes. Some of these icy bodies represent the faintest, tiniest objects ever directly observed at just 3 miles across.
These findings provide a fresh look at planetesimals, which serve as the fundamental building blocks of planets. Planetary scientists previously expected the smallest TNOs to show significantly more evidence of collisions than their larger counterparts.
Repeated impacts theoretically should have broken up their surfaces and mixed their materials thoroughly. That process would have produced distinct colour variations and varied chemical compositions across the population.
Small Objects Retain Ancient Surface Composition Despite Missing Planetesimals
Instead of showing disruption, the small objects largely follow the same colour relationships seen among much larger TNOs. Because colour provides direct clues to surface composition, this uniformity suggests their surfaces have changed surprisingly little since the dawn of the planetary system.
At the same time, the research team uncovered fewer tiny TNOs than some existing models of planet formation predict. The discrepancy points toward gaps in current theoretical frameworks regarding how dust and ice coalesced.
“It’s really fascinating to see that the smallest objects are somehow ‘remembering’ and preserving the history of how they were made,” said lead author Anastasia Morgan of Northern Arizona University.
Deeper Observations Planned with JWST
The research team is already planning deeper observations to resolve the missing population puzzle. Future JWST campaigns could search for TNOs as small as 1km across.
Pushing the detection limit down to 0.6 miles across could potentially provide an even clearer picture of how the Solar System’s planetary building blocks formed.
