If you go far enough from the Sun, the Solar System becomes much more populated. Beyond Neptune’s orbit lies the Kuiper Belt, a vast ring of icy rock. Cold and dark, there’s Pluto, Arrokot, and countless smaller objects.

They’re known as Kuiper Belt Objects, or KBOs, and astronomers have discovered signs of an unexpected increase in density between 70 and 90 AU from the Sun, separated by a large, nearly empty void between the inner KBO and the population. Closer to the Sun. It almost looks like there are two Kuiper belts, or at least two components, which is something no one expected to find.

“If confirmed, this would be a major discovery,” says planetary scientist Fumi Yoshida of the University of Occupational and Environmental Health Sciences and Chiba Institute of Technology in Japan. “The primordial solar nebula was much larger than previously thought, and this could be important for studying the process of planet formation in our solar system.”

Objects in the Kuiper Belt are believed to represent the most pristine material our Solar System contains. The belt itself extends from the orbit of Neptune, approximately 30 AU from the Sun (one AU is the average distance between the Earth and the Sun), to approximately 50 AU from the Sun.

This distance from the Sun means that everything within the Kuiper Belt is only minimally affected by solar radiation, meaning that KBOs have likely remained largely unchanged since the birth of the Solar System, about 4.6 billion years ago. These objects are ancient remnants of the cloud of matter known as the solar nebula, from which the Sun and planets formed.

The New Horizons spacecraft is heading deeper into the solar system after passing Pluto in 2015; at the time of writing, the spacecraft was located almost 60 astronomical units from the Sun. To support ongoing research into the outer solar system, astronomers on Earth are observing the Kuiper Belt with Japan’s National Astronomical Observatory’s Subaru Telescope in Hawaii.

To date, Subaru observations have detected 263 new KBOs, but a large international team of astronomers led by Wesley Fraser of the National Research Council of Canada found that 11 of these objects are much, much farther away than we thought the Kuiper belt ended — more than 70 astronomical units outside the region.

Based on the number of objects observed, the researchers were able to estimate the density of the outer ring of the Kuiper belt. It would be lower than the inner population but high enough to form new structure. However, almost nothing was found in the region between 55 and 70 AU. It may seem strange, but such a gap is a feature we see in other planetary systems, and it brings the Solar System more in line with what we find elsewhere in the galaxy.

“Our Solar System’s Kuiper Belt was long thought to be very small compared to many other planetary systems, but our results suggest that this idea may simply be due to observational bias,” Fraser explains. “So perhaps if this result is confirmed, our Kuiper Belt is not so small and unusual compared to those around other stars.”

Many of our observations of the Milky Way galaxy indicate that our solar system is unusual in many ways. Since the Solar System is the only known planetary system that supports life, these oddities may be factors in the Solar System’s suitability for life.

But our space-observing technology has limitations that can lead to significant observational errors, suggesting features that don’t actually exist. If the new Kuiper belt observations are confirmed, we’ve eliminated one of those features, an extremely small solar nebula. The observations continue to track the orbits of 11 more distant objects to shed more light on discovery.

“This is a groundbreaking discovery that reveals something unexpected, new and exciting in the far reaches of the solar system,” said Alan Stern, New Horizons principal investigator from the Southwest Research Institute. “This discovery would not have been possible without the world-class capabilities of the Subaru Observatory.” The study acknowledged Planetary Science Journal and is available on arXiv.