A joint investigation by NASA’s two powerful space telescopes has uncovered previously unknown objects beyond Neptune, offering scientists a rare opportunity to study the ancient building blocks of planets.

Astronomers have uncovered important clues about the early history of the solar system after combining observations from NASA’s Hubble Space Telescope and James Webb Space Telescope. The research identified 27 previously unknown objects beyond Neptune, revealing surprising details about their sizes, surface characteristics and formation history.

These distant bodies, known as trans-Neptunian objects (TNOs), are small, icy remnants that orbit the Sun beyond Neptune. Many have survived for billions of years, making them valuable natural records of the conditions that existed when the solar system was taking shape.

The findings were published in two research papers in The Astronomical Journal in September 2026. The observations provide one of the deepest investigations yet of these extremely faint objects.

Ancient Remnants of Planet Formation

Scientists believe the planets developed from a vast disk of dust and small particles surrounding the young Sun. Over time, these materials collided and gradually accumulated into larger bodies known as planetesimals.

These early objects eventually became the foundations of planets, moons and other solar system bodies.

Beyond Neptune, however, many planetesimals never developed into larger worlds. Instead, they remained as relatively small frozen objects in the distant outer solar system.

Because these bodies have experienced billions of years of cosmic history, studying them can help researchers reconstruct the processes that shaped the planetary system.

Two Space Telescopes, One Major Discovery

The research teams combined observations from Hubble and Webb to investigate a distant region of the sky.

Hubble captured visible light from the objects, while Webb collected infrared observations. Using both types of data allowed astronomers to estimate the objects’ sizes, study their surface colours and examine their orbital characteristics.

The 27 newly identified objects are exceptionally faint. Many are more than 100 million times dimmer than objects visible to the unaided human eye.

One of the smallest objects measured approximately five kilometres across. Detecting such a faint body demonstrates the sensitivity of modern space-based observatories.

The discoveries were made through research teams associated with the University of Victoria in Canada, the National Research Council of Canada and Northern Arizona University.

Tiny Objects Preserve Unexpected Surface Clues

One of the most surprising findings concerned the colours of the distant objects.

Astronomers had expected smaller TNOs to show different surface characteristics from larger ones. Over billions of years, repeated collisions could break these bodies apart, expose fresh material and change their surface compositions.

However, the observations revealed that the smaller objects generally followed colour patterns similar to those of their larger counterparts.

This suggests that their surfaces may have preserved much of their original chemical character.

Scientists are considering several explanations. These objects may have experienced fewer collisions than previously predicted, or their surfaces may retain traces of their original composition even after being struck or fragmented.

The result provides a new opportunity to investigate how material in the early solar system changed over time.

Scientists Find Two Populations with Similar Size Patterns

The study also examined two broad groups of trans-Neptunian objects, commonly described as dynamically cold and dynamically hot.

These labels refer to their orbital behaviour, not their physical temperatures.

Cold objects generally follow more circular orbits and remain closer to the main plane of the solar system. They are thought to have stayed relatively close to their original formation regions.

Hot objects have more elongated and inclined orbits. Researchers believe many formed closer to the giant planets before being pushed into more distant regions as the early solar system evolved.

Despite their different histories, the two populations displayed surprisingly similar size distributions.

This observation raises important questions about how planetesimals formed in different regions of the young solar system. It may indicate that some planet-building processes operated in comparable ways despite differences in the surrounding conditions.

Fewer Small Worlds Than Expected

Webb’s observations also revealed a shortage of very small trans-Neptunian objects compared with predictions from some existing planet-formation models.

This difference could help researchers improve their understanding of how dust and pebbles combined to create larger planetary building blocks.

Scientists will need additional observations and theoretical work to determine why the number of small objects appears lower than expected.

The discovery does not mean that these objects are absent from the outer solar system. Rather, it highlights a gap between some theoretical predictions and the population detected in this deep survey.

A New Opportunity to Understand the Solar System

The findings demonstrate the scientific value of combining different space observatories. Hubble’s visible-light observations and Webb’s infrared capabilities provide complementary information that would be difficult to obtain through either telescope alone.

By studying distant icy bodies, astronomers can investigate material that has remained relatively unchanged since the solar system’s early development.

The research could eventually help answer fundamental questions about how planets formed, how the giant planets moved through space and why different regions of the solar system contain distinct populations of small objects.

As observations continue, these frozen worlds beyond Neptune may provide an increasingly detailed record of the processes that shaped the planetary neighbourhood billions of years ago.