What is the Kuiper Belt?

It's three billion miles away, but getting to grips with the Kuiper Belt could help scientists understand a lot more about our universe

23 Oct 2017
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The universe holds many mysteries and the Kuiper Belt, a whizzing collection of millions of icy objects orbiting the Sun that starts three billion miles away, is no exception. This belt has alluded scientists for years and the mysteries contained within it are difficult to comprehend. Here is everything you need to know about the strange, mysterious enigma.

What exactly is the Kuiper Belt?

Scientists think the Kuiper Belt could hold the clues to the origins of our solar system, which lies beyond the orbit of Neptune. The thing is, we don’t really know what’s going on there, simply because the icy matter is not big enough to observe. The Belt is billions of miles away from the Sun, making it difficult to see with the best telescope, so you can understand why astronomers are struggling to decipher its mysteries.

The Kuiper Belt is made of the same stuff that kicked off the planetary formation. Now, outside of the gravitational forces constructed the biggest planets, the leftovers are mainly clumps of floating ice.

The Kuiper Belt is made up of mostly ice-based objects rather than the rock-based asteroids that lie in the Asteroid Belt, between Mars and Jupiter. Estimates say the Kuiper Belt is 20 times the size of the Asteroid Belt.

The objects in the Kuiper Belt can be grouped into two categories. These are cold Kuiper Belt objects, with round and circular orbits similar to planetary orbits, and hot objects, which loop well out of the orbital plane of the cold objects.
Pluto is the largest and most famous member of the Kuiper Belt. Its eccentric orbit makes puts it in the ‘hot’ category and it is one of three dwarf planets in the belt, the other two being Haumea, another hot one, and Makemake, a cold Kuiper Belt object.

Alongside the icy remnants there are also wild, untamed objects beyond Neptune in the group known as the scattered disk. These objects pass in elliptical orbits, coming much closer and stretching farther from the Sun than the Kuiper Belt objects. Aros, which is slightly larger than Pluto, is found in the scattered disk, orbiting from the back ends of the solar system.

The scattered disk and the hot objects most likely started out near Jupiter, at the birth of the solar system. As the giant planets migrated away from the Sun, the theory goes, the scattered disk and hot objects were knocked into their orbits by the gravity of the planets.

More than a thousand objects have been discovered in the Kuiper Belt and there’s predicted to be tens of thousands more. It’s difficult to determine the chemical composition of these objects because they’re so far away and so small. Spectrographic studies suggest the objects are composed of ices, light hydrocarbons like methane, ammonia and water ice with a wide gamut of different colours. This suggests their composition is very similar to Pluto.

A Short History of the Kuiper Belt

The bits of debris that make up the Kuiper Belt could have been the beginnings of a planet that failed to materialise thanks to Neptune’s gravity getting in the way.

In 1943, astronomer Kenneth Edgeworth proposed the idea that the material beyond Neptune was too widely spaced out to be condensed into planets so instead, was forced to condense into smaller clusters of objects.

In 1951, Gerard Kuiper predicted the existence of the Kuiper Belt, saying it formed in the early solar system. He said it was this was where comets come from, which turned out to be true, and why there are no larger planets outside the inner solar system.

Then in 1992, after five years of searching the outer solar system, astronomers David Jewitt and Jane Luu announced the discovery of the first ever Kuiper Belt object, 15760 1992 QB1. Six months later, the second discovery was made in roughly the same region as the first and this set off the discovery of the thousands of objects in the Kuiper Belt we know of now.

Much debate has been made over what to call the Belt with names like Edgeworth-Kuiper Belt being floated, alongside the more common Kuiper Belt and the Trans-Neptunian Object (TNO).

Our solar system isn’t special though. It turns out that there are other Kuiper Belts orbiting other star systems, as wide as up to 50 times the distance between Earth and the Sun.

New Horizons Space Probe and MU69

The New Horizons probe was built to observe Pluto, it’s moons and the Kuiper Belt.

The probe was put into hibernation on 7 April but was woken up temporarily for a burst of activity in September, as it travels the long journey to the Kuiper Belt and to a targeted object of 2014 MU69. The team at NASA will begin performing checks and collecting data for the next three months as well as correcting the flight plan. It will then return to hibernation until its planned encounter with MU69 in 2019.

MU69 is a billion miles away from Pluto and four billion miles away from Earth, so it has been a long journey for the New Horizons space probe.

Planet 9

The mounting evidence for the existence of a ninth planet has evidence that is supported by the Kuiper Belt. The mass of the planet is suspected to be causing observable irregularities in the movement of the bodies of ice within the belt.

The Mysteries of the Kuiper Belt

While they may be billions of light years away, nebulae, stars and black holes are massive. When you compare them to the objects in the Kuiper Belt, in our own solar system, these objects are just specks of dust.

You can look at a mountain that’s a hundred miles away and know more about it than a tennis ball that’s one mile away. That’s why the Kuiper Belt holds so many mysteries; we know almost nothing about it because of how difficult it has been to observe.

Hopefully, though, as the New Horizons gets closer to the Kuiper Belt and to MU69, we’ll discover many new things about the Kuiper Belt that has alluded us for so long. Keep your eyes peeled and hang on for 2019.

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