Hubble and James Webb Space Telescopes Spot 27 Icy Relics Beyond Neptune
“It’s really fascinating to see that the smallest objects are somehow ‘remembering’ and preserving the history of how they were made,” lead author Anastasia Morgan of Northern Arizona University said about a discovery published on September 8, 2026, in The Astronomical Journal. Astronomers combined observations from the Hubble Space Telescope and the James Webb Space Telescope to study 27 newly discovered trans-Neptunian objects orbiting the Sun beyond Neptune.
These distant, icy bodies serve as pristine planetesimals, acting as the fundamental building blocks of planets. Researchers expected that smaller trans-Neptunian objects would show far more evidence of surface collisions than their larger counterparts. Repeated impacts should have broken up these surfaces and mixed their materials over billions of years, producing distinct colours and compositions.
Colour Analysis Reveals Untouched Primordial Surfaces
Contrary to scientific models, the tiny objects largely follow the exact same colour relationships seen among much larger trans-Neptunian bodies. Because surface colour provides direct clues to composition, this uniformity indicates that the objects have changed surprisingly little since the formation of the Solar System. The objects in the sample ranged in diameter from about 5 kilometres, marking the smallest bodies detected, up to approximately 80 kilometres.
The research teams utilized Hubble to observe visible light while employing Webb to capture infrared light from the same region beyond the blue ice giant. This dual-telescope method allowed scientists to measure sizes, orbits, and surface colours spanning 0.35 to 3.2 micrometres. The investigators identified two distinct populations among these bodies. Dynamically cold trans-Neptunian objects remain in relatively circular orbits close to the plane of the solar system, whereas hot trans-Neptunian objects formed closer to the giant planets before Uranus and Neptune migrated outward.
Size Distribution Defies Planetary Formation Predictions
Alongside the colour findings, the research uncovered fewer tiny trans-Neptunian objects than established planet formation models predicted. Webb successfully detected objects as small as roughly five kilometres across, with the smallest being approximately five times smaller than the faintest object detectable by ground-based telescopes. The findings suggest that destructive collisions may occur far less frequently in the outer Solar System than astronomers previously anticipated.
The research was conducted by two separate teams of doctoral candidates from Northern Arizona University and the University of Victoria. The Morgan group utilized 99 Hubble orbits at nine different points covering 65 percent of Webb’s field of view, recovering 13 of the objects initially discovered by Webb’s NIRCam instrument. The teams plan to conduct deeper observations using future telescope time to search for even smaller bodies measuring down to one kilometre across.
Frequently Asked Questions About Trans-Neptunian Objects
How far away are the newly discovered objects?
The newly discovered bodies orbit the Sun beyond the orbit of Neptune, inhabiting the distant regions of the outer Solar System such as the Kuiper Belt.
What instruments were used in the discovery?
Astronomers combined observations from NASA’s James Webb Space Telescope, which performed the initial infrared discoveries, and the Hubble Space Telescope, which captured optical data.
When were the research findings published?
The findings were published in two companion papers in The Astronomical Journal on September 8, 2026.
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