Astronomers are getting closer to the secrets of the Kuiper Belt

beyond beyond Neptune’s orbit lies in a vast ring of ancient ruins, dynamic mysteries, and perhaps a hidden planet — or two.

the Kuiper beltA region of frozen debris about 30 to 50 times farther from the sun than Earth — and perhaps farther, though no one knows — has been shrouded in mystery since it first appeared in the 1990s.

Over the past 30 years, astronomers have cataloged about 4,000 Kuiper Belt Objects (KBOs), including a small collection of dwarf worlds, icy comets, and remaining planetary fragments. But this number is expected to increase tenfold in the coming years with an influx of observations from more advanced telescopes. In particular, the Vera C. Rubin Observatory in Chile will illuminate this obscure area with its flagship project, the Legacy Survey of Space and Time (LSST), which began operating last year. Other next-generation observatories, such as the James Webb Space Telescope (JWST), will also help focus on the belt.

“Beyond Neptune, we have a census of what’s in the solar system, but it’s a patchwork of surveys, leaving a lot of room for things that might be there that have been missed,” says Renu Malhotra, who is the Louis Foccart Marshall Research Professor of Science and professor of planetary science at the University of Arizona.

“I think that’s the big thing that Rubin will do, is fill in the gaps in our knowledge of the contents of the solar system,” she adds. “This will greatly advance our population and knowledge of the contents of the solar system.”

As a result, astronomers are bracing for a deluge of discoveries from this new frontier, which could shed light on a host of outstanding questions. Are there new planets hidden in the belt, or lurking beyond it? How far does this area extend? And are there traces of past cataclysmic encounters between worlds – whether local or from interstellar space – imprinted in this largely pristine collection of objects from the deep past?

“I think this is going to become a very hot field very soon, because of the LSST,” says Amir Siraj, a graduate student at Princeton University who studies the Kuiper Belt.

The Kuiper Belt is a graveyard of potential planets that were scattered away from the Sun during the solar system’s chaotic birth about 4.6 billion years ago. Pluto was the first Quibe Belt object ever observed, more than half a century before the Belt itself was discovered.

Since the 1990s, astronomers have discovered a handful of other dwarf planets in the belt, such as Eris and Sedna, as well as thousands of smaller objects. Although the Kuiper Belt is not completely static, it is a mostly intact time capsule of the early solar system that can be mined for clues about planetary formation.

For example, the belt contains strange structures that may be signatures of past encounters between giant planets, including a particular group of objects, known as the “core,” located at about 44 astronomical units (AU), where AU is the distance between Earth and the Sun (about 93 million miles).

While the origin of this nucleus remains unexplained, one popular hypothesis is that its constituent objects — known as cold classical — were drawn in by Neptune’s outward migration through the solar system more than 4 billion years ago, which may have been a bumpy ride.

The idea is that “Neptune got jolted by the rest of the gas giant planets and made a little jump; this is called the ‘Neptune jump’ scenario,” says Wes Fraser, an astronomer at the Canadian National Research Council’s Dominion Astrophysical Observatory, who studies the Kuiper Belt. Astronomer David Nesvorny I came up with this idea.