Evrim Yazgin
Cosmos science journalist
NASA’s New Horizons Kuiper Belt search has revealed a population of objects in the outer solar system which suggest the solar system formed from a much larger protostellar disc than originally thought.
The Kuiper Belt is a region beyond Neptune populated by ancient remains of planetary building blocks. It was first discovered in the 1990s.
Among the icy objects in the Kuiper Belt are dwarf planets such as Pluto and Quaoar.
Such belts are common around stars with planetary systems around the galaxy.
The Kuiper Belt’s main region begins from Neptune’s orbit about 4.5 billion km from the Sun. This is about 30 times further away from the Sun than Earth, or 30 astronomical units (AU). It extends to about 50 AU.
Much of this region of space remains unknown.
Research using data from the 8.2-metre Japanese Subaru Telescope in Hawai‘i shows a group of icy objects in the Kuiper Belt at 90 AU.
The findings are published in the Planetary Science Journal of the American Astronomical Society. A preprint of the paper can be read here.
This means that the Kuiper Belt extends far beyond what was previously believed.
It also suggests that NASA’s New Horizons space probe – currently at about 60 AU from the Sun – which launched in 2006 has not yet reached the outer rim of the Kuiper Belt object.
“Our solar system’s Kuiper Belt long appeared to be very small in comparison with many other planetary systems, but our results suggest that idea might just have arisen due to an observational bias,” says lead author Wes Fraser, co-investigator on the New Horizons mission science team from the National Research Council of Canada.
“Our Subaru observations searched down to fainter detection limits and found a significant Kuiper Belt mass at 70 to 90 times as far from the Sun as Earth. So maybe, if this result is confirmed, our Kuiper Belt isn’t all that small and unusual after all, compared to those around other stars.”
It’s possible that these more distant Kuiper Belt objects have been pushed into their orbit by Neptune’s gravity. But their presence could also mean scientists need to rethink current models of the solar system’s formation.
The disc of planetary material which led to the formation of the planets and other structures in the solar system 5 billion years ago could be larger than previously thought.
“We still have much to learn about what this distant population actually looks like, but what’s fascinating is that there is a new Kuiper Belt population out there at all,” Fraser adds.
