11 Kuiper Belt facts you need to know

The Kuiper belt is one of the most interesting parts of the solar system. It’s where four of the five dwarf planets reside, and a whole lot else is out there too. Although we know more about the Kuiper belt now after the New Horizons mission to Pluto, there’s still a whole lot we don’t know about it. 

But what do we know now? Well, let’s take a look at some of the things we do know about the Kuiper belt. I also have some cool facts to share with you too, so let’s get started!


Kuiper Belt Facts

  1. The Kuiper belt was first theorized back in 1951 by a Dutch planetary scientist named Gerard Kuiper. He’s a big part of why we know what we do today, and he knew what the moon would feel like before we even went there!
  2. One of the most interesting Kuiper belt facts is that it’s actually where many comets originate – we also think that comets come from the Oort cloud, which is even further away from the Sun than the Kuiper belt.
  3. What’s another name for it? Well, many astronomers will refer to it as the trans-Neptunian region, which means the region past the planet Neptune. So sometimes you’ll see objects there referred to as KBOs (Kuiper Belt Objects) or TNOs (Trans Neptunian Objects).
  4. Even NASA refer to the Kuiper belt as a “donut”, which is probably the best way to explain it!
  5. There are hundreds of millions of icy objects out in the Kuiper belt. Astronomers think that these are essentially the leftovers and remains of the formation of our solar system.
  6. We think that the remnants out in the Kuiper belt would have come together to form another planet, however the gravity from Neptune has prevented this from happening.
  7. At the moment, we only have a few thousand objects from the Kuiper belt that have been identified and catalogued by astronomers. There are hundreds of thousands more out there for us to find!
  8. Even though there are tons of objects out there, we don’t think that they total up to any more than 10% of the Earth’s mass. That’s how huge the Earth is!
  9. The Kuiper belt is more than 20x wider than the Asteroid belt, and up to 200x bigger than it too.
  10. The New Horizons mission from Earth to Pluto took 9.5 years for it to make it there – that’s how long it took to get to the Kuiper belt from Earth!
  11. Although we knew that the Kuiper was probably out there in the 1950s, it was until 40 years later that we actually found the first KBO. After this in 1992, thousands more KBO’s have been found.

Where is the Kuiper belt?

Many people misunderstand exactly where the Kuiper belt is. If you look at this picture, then you’ll be able to see it easily – it’s actually at the edge of everything in the outer solar system, even further from the Sun than Neptune is! 

Map showing the location of the Kuiper Belt

What’s in the Kuiper belt?

Another common question people ask about the Kuiper belt is what’s exactly out there! Well, we have four of what we typically classify as “dwarf planets” out there. These are;


Pluto was discovered in 1930. This was more than 20 years before the Kuiper belt was even theorized by astronomers!



Originally the 10th planet, the discovery of Eris was one of the reasons why astronomers decided to split planets into two categories; planets, and dwarf planets.



Haumea, the famous oval dwarf planet, isn’t spherical. Astronomers say that it was hit by another object billions of years ago, which caused it to rotate faster – making it oval!



Makemake is another dwarf planet that was discovered in a similar timeframe to Eris and Haumea. It has one moon nicknamed MK 2, which astronomers discovered in 2016.

As well as these dwarf planets, there’s actually a lot more out there in the Kuiper belt. According to NASA, there are more than a trillion comets out there in the Kuiper belt. As well as this, there’s actually supposedly more than 100,000 different objects out there that are larger than 100km!

More Commonly Asked Questions about the Kuiper Belt

What’s the difference between the Kuiper belt and the Asteroid belt?

The Asteroid belt and the Kuiper belt are similar in the fact that they pretty much hold all of the leftovers from the rest of the solar system, objects dating back to billions of years ago. Whilst the Kuiper belt is situated past Neptune, the Asteroid belt is situated between Mars and Jupiter.

Are there more dwarf planets out there in the Kuiper belt?

There are definitely more dwarf planets out there, and there are even some that we have even identified already. Objects like Quaoar meet all of the classifications of a dwarf planet, but it just hasn’t been processed yet by astronomers, which can take many years. It’s likely in the not too distant future that we’ll see many more dwarf planets added to the list. However saying this, we’ve known about Quaoar since 2002 and it’s still not a dwarf planet, so no guarantees!

How many Kuiper belt objects (KBOs) are there?

Although we have only identified thousands of KBOs, we are sure that there are many more of them out there Astronomers think that there are millions of more objects out there in the Kuiper belt to be discovered.


How long would it take us to get to the Kuiper belt from Earth?

As menitoned, the New Horizons mission took us almost 10 years to make it from Earth to Pluto. However, this was travelling at varying different speeds; when it left Earth, it was travelling at 36,373mph. Later, it was reported that the spacecraft reached maximum speeds of over 53,000mph when they reached the Kuiper belt. If it took a decade to make it there at this speed, imagine how long it would take for a human to travel this far at normal speeds!

What are the objects in the Kuiper belt made of?

Another great question. We know that many of the objects in the Asteroid belt are made up of rock and metal. With what we know about the Kuiper belt so far, we think that most of the objects out there are made primarily of rock and ice, due to it’s long distance from the Sun.


All in all, the Kuiper belt remains one of the most important things that we’ve learned about astronomy in the past century. The more that we learn about the Kuiper belt, the more that we learn about our Solar System in general. 

Even though there are many more objects out there to discovered beyond the realms of Neptune, we know now so much more than we did even a few decades ago.