The Hubble and James Webb space telescopes have uncovered 27 new Trans-Neptunian Objects (TNOs), which are small icy bodies that orbit the sun far beyond Neptune. These objects are all less than 25 miles (40 kilometers) in diameter, with the smallest being only about 6 miles (10 kilometers) wide. TNOs are remnants from the early solar system, some of which never grew large enough to become planets. They are found in the distant Kuiper Belt and other regions beyond Neptune. Scientists expected these TNOs to have been altered by impacts over time, which would mix their surfaces and change their color and composition. However, a study led by Anastasia Morgan of Northern Arizona University and Marielle Eduardo of the University of Victoria found that the surfaces of these small TNOs appear largely unchanged since their formation. This suggests that the objects have remained pristine despite being in space for billions of years. TNOs can be divided into two main groups based on their orbits. Those native to the Kuiper Belt have nearly circular orbits and are aligned with the ecliptic plane, the plane in which the planets orbit the sun. In contrast, some TNOs formed closer to the giant planets but were ejected into the Scattered Disk, where they now have elongated, tilted orbits. These are called dynamically "hot" TNOs. Surprisingly, even these hot TNOs show no signs of surface changes caused by impacts, according to David Trilling of Northern Arizona University. This finding raises two possibilities: either there are fewer impacts in the distant reaches of the solar system than previously thought, or impacts do not significantly alter the surfaces of small TNOs. Using the James Webb Space Telescope's infrared capabilities, Marielle Eduardo determined the size distribution of these TNOs. Infrared observations allow scientists to measure the size of distant objects based on their brightness. The results showed fewer very small TNOs than predicted by current models of planetesimal formation. Eduardo noted that the process of forming planetesimals, the building blocks of planets, seems to produce similar size distributions for both cold and hot TNOs, even though they formed in different regions of the early solar system. This suggests that the formation process is not strongly affected by the conditions of the disk in which they formed. The TNOs are extremely faint, with brightness levels between magnitudes 24.1 and 29.3—comparable to seeing a group of fireflies on the moon from Earth. The findings were published in The Astronomical Journal as two separate papers on September 8, one focusing on the color and composition of the TNOs, and the other on their size distribution.