Kuiper Belt

In 1992, two researchers, David C. Jewitt and Jane X. Luu from the University of Hawaii, made a fascinating find. They spotted a small object, named 1992QB1, circling the Sun beyond Neptune, our eighth planet. Since their discovery, we’ve found over 3,100 similar objects in that same zone. Scientists believe there could be millions of icy bodies there, with many spanning over 60 miles (100 kilometers) wide.

This vast cluster of space objects is named the Kuiper Belt as a nod to Gerard Kuiper, a Dutch-American astronomer. In the 1950s, he suggested there might be bodies beyond Neptune. Interestingly, Kenneth Edgeworth, another astronomer, had also talked about objects beyond Pluto in the 1940s. Some people call it the Edgeworth-Kuiper Belt to honor them both.

The Kuiper Belt is like a giant icy doughnut, circling the edge of our solar system. It’s full of icy objects that are mixed with rock and other frozen compounds like ammonia and methane.

Icy bodies in the Kuiper Belt are named “Kuiper Belt Objects” or KBOs. The most famous KBO? Pluto. In fact, Pluto’s demotion from planet status happened because we found thousands of KBOs right there with it.

Back in 1930, Pluto was the first KBO we found. It was a surprise because, at that time, no one expected a bunch of icy worlds beyond Neptune. Now, Pluto has a title: the “King of the Kuiper Belt.” It’s the biggest thing out there, but there’s another object, Eris, that’s close in size yet weighs a bit more.

Think of the asteroid belt between Mars and Jupiter. The Kuiper Belt is a lot like that, but on a grander scale. Both belts are made of ancient leftovers from when our solar system was born 4.6 billion years ago. Yet, the Kuiper Belt is massive. It’s up to 20 times wider and can be 100 times heavier than the asteroid belt.

Had Neptune not existed, the objects in the Kuiper Belt might have combined to form a planet. But Neptune’s strong gravity prevented that. It disturbed the space around so much that the icy bodies couldn’t merge into a big planet.

Today’s Kuiper Belt might be just a shadow of its past. Some scientists believe that long ago, the big planets like Jupiter, Saturn, Uranus, and Neptune changed their orbits. When they did, they might have flung away a lot of the Kuiper Belt’s material—perhaps as much as 7 to 10 Earths’ worth.

To understand distances in space, astronomers use “Astronomical Units” or AU. One AU is roughly the space between Earth and the Sun. The Kuiper Belt starts 30 AUs from the Sun and extends to about 50 AUs. However, a part of it, the “scattered disc,” reaches up to 1,000 AUs. This makes the Kuiper Belt one of the biggest structures in our solar system.

Beyond the Kuiper Belt, there might be another, even more distant group of icy bodies. Scientists refer to this place as the Oort Cloud. They think of it as a vast, ball-shaped shell. It wraps around the Sun, planets, and Kuiper Belt Objects.

Meanwhile, the Kuiper Belt is wearing down. The objects there sometimes crash into each other. These crashes create smaller fragments, comets, and dust. This debris then gets swept out of the solar system by solar winds.