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Kuiper Belt / Trans-Neptunian Objects

Kuiper Belt and the Oort Cloud are two regions in space that encircle our solar system. The Kuiper Belt contains thousands of asteroids that orbit The Sun outside Neptune`s orbit. Although asteroids and rocks are more associated with the Kuiper Belt, comets are thought to exist there. The most famous comet of them all, Halley`s Comet Aphelion is past Neptune at which point it then turns back and heads towards the Sun.

The Oort Cloud on the other hand has not been proven to definately exist as yet unlike the Belt. To give some idea of where everything is, have a look at the picture below.

The Kuiper Belt is similar to the Asteroid Belt that mainly straddles the area between the planets of Mars and Jupiter. The Kuiper Belt spreads out much further than the Asteroid belt. The objects in the Kuiper Belt are normally referred to as Trans-Neptunian Objects because they orbit outside the orbit of Neptune. The composition of the objects in the asteroid belt and the kuiper belt are different. The asteroid belt, the asteroids are made of rock and metal where as the objects in the Kuiper Belt are frozen material such as methane, amonia and water. Ref: Wiki

Picture of Sedna and it location

In the picture, copyrighted N.A.S.A., you will see from the picture just how distant these things are from us.

Discovery of the Kuiper Belt

In an area just beyond Neptune lies the Kuiper Belt, an area that contains thousands of asteroids. It is named after Gerard Peter Kuiper, a Dutch Born American Astronomer ( Dec 7, 1905 - Dec 23, 1973) who suggested the existance of the Belt. His theory was not confirmed until August 30, 1992 with the discovery of 1992 QB1 object.

It has never been given any other name apart from its original designation. The discoverers wanted to call it Smiley but as there was already an object out there with that name, they declined to give it another name. The object was discovered by David Jewitt and Jane Luu who had been searching space since 1987 on and off and finally with the help of the University of Hawaii`s 2.2m telescope they found what they were looking for. The object was further out than Pluto.Ref: N.A.S.A.

Kuiper Belt Objects are also known as Trans-Neptunian Object as they orbit the orbit further out than Neptune. Its existance had first been put forward by Irish Astronomer Kenneth Edgeworth but he`s received little or no recgonition of this. ref:Britannica

Difference between the Kuiper Belt and the Oort Cloud

The most important difference between the top is that the Kuiper Belt is known to exist. The Oort Cloud is a theory that has not yet been proved or disproved. The Kuiper Belt consists of asteroids and dwarf planets whilst the Oort Cloud will also include comets before they are sent on their way towards the Solar System.

There is no clear distinction between where the Kuiper Belt ends and where the Oort Cloud begins. The current locations of both are, the Kuiper Belt is just outside Nepturne, at about 50 times the distance betwen the Earth and the Sun and the Oort Cloud is about a light year away. The objects of the Oort Cloud are small, our telescopes are far too small for us to see any.


Pluto and Sedna aren`t the only interesting objects in the Kuiper Belt. Haumea, a fast spinning egg-shaped object. It is believed that it was sent spinning as the result of a collision in the early days. It spins end over end every four hours. The object has two moons Hi`iaka and Namaka. Ref: N.A.S.A.

Sedna and Pluto

Sedna was at one time referred to as The Solar Systems tenth planet. However since then, its claim to that stature has diminished. It is three times the distance from the Sun as Pluto and people are questioning as to whether it is part of the Kuiper Belt or not.

There has been a debate as to what constitutes a planet, some saying Sedna is a planet and some saying that Pluto should no longer have that stature. The International Astromoner Union, the overaching authority on all things with space tried to create a set of rules to determine what a planet is. The description proved controversial and it resulted in Pluto being downgrading as a planet to a dwarf planet in 2006. Ref: I.A.U.

Given Sedna`s location being so far from the Sun but not nearly as far as where the Oort Cloud is supposed to be, astronomers are wondering if there is another belt, an `Inner Oort Cloud`. Sedna is about 8 billion miles away from the Sun. Ref: Caltech. To put Sedna in to prospective, Pluto is about 3.67 billion miles away. Ref: Caltech

Pluto was the first Kuiper Belt Object discovered but was classed as a planet because other Kuiper Belt Objects had not yet been discovered. Pluto was downgraded when the KBO Eris was discovered and that it was believed that Eris was bigger than Pluto. Eris was originally called Xena and its moon called Gabrielle but was changed so that it was in line with naming other planetoids, that is being named after ancient gods. Eris has now been calculated to be 2,326 kilometers in diameter and Pluto is 2,300 kilometers Ref: Planetary . In terms of size, the two objects are not much different but it was the fact that Sedna was believed to be bigger that helped downgrade Pluto.

If you have a powerful telescope and want to know where to look, the following picture will give you an idea where to point the lense. The time given is in Pacific Standard Time, you will need to adjust depending on where in the world you are.

Rough location of where Sedna is in the night sky

The hunt for the Nineth Planet

The hunt for the new nineth planet after Pluto was downgraded is in full swing. It has been noted that some kuiper belt asteroids are travelling differently to how they are supposed to be. The fact that they are is possibly down to a large planet on the outskirts of our solar system. Its orbit take it out to the far depths of outer space which is why its not been seen. The diagram released by artists at Caltech and NASA show the likely path that the planet takes around the Sun.

N.A.S.A. has taken to using the might of the internet and is calling on amateur astronomers to help through the Backyard Worlds project. The task involves going through thousands of photos and looking for any changes that might indicate a planet or something. It is exactly how Clyde Tombaugh discovered Pluto.

Rumoured orbit of the new nineth planet.

Kuiper Belts around other Stars

In 2006, it was revealed that two stars HD 53143 and HD 139664 were discovered to have their own versions of the Kuiper Belt. Both stars are relatively close to us, a mere 59.77 and 57.87 light years away from us respectively. Ref: Universe Today

In addition to having an Extrasolar Planet (Exoplanet), the star that we know as Fomalhaut in the southern hemisphere is reckoned to have a its own kuiper belt. Fomalhaut`s Kuiper Belt is a little further out from its star than ours. Our Kuiper belt is 50 A.U. from the Sun, in plain English, that means it is fifty times the distance between Earth and the Sun. Fomalhaut`s kuiper belt is 133-158 times the distance from its Sun. It is well know that Fomalhaut has one planet but this discovery increases the chances that the star has multiple planets in orbit. ref:Sky and Telescope

New Horizons Space Probe

Now that New Horizons space probe primary mission was to Pluto has been achieved, the space probe`s life isn`t over yet. New Horizons has been given a new target to head towards, the new target is 2014 MU69 which it is expected to fly by in 1st Jan 2019 so not celebrating the night before for the ground crew. Ref: N.A.S.A

Different Type of Asteroids in the Kuiper Belt

There are a number of different types of objects in the Kuiper Belt, a Plutino is an asteroid that for every two orbits that Neptune makes, the Plutino makes three. It doesn`t specify any physical features on the object, just its path round the Sun however distant. Ref: Plutino

The below table gives brief details of well known Kuiper Belt objects.

NameDiscoverDiscovery DateCategory
OrcusM.Brown, C. Trujillo, D. Rabonowitz17 February 2004Plutino
IxionDeep Ecliptic Society22 May 2001Plutino
SednaM.Brown, C. Trujillo, D. Rabonowitz14 November 2003Trans-Neptunian
DeucalionDeep Ecliptic Survey18 April 1999Trans-Neptunian
RhadamanthusDeep Ecliptic Survey17 April 1999Trans-Neptunian
ChaosDeep Ecliptic Suvey19 November 1998Kuiper Belt
VarunaR. McMilan28 November 2000Kuiper Belt
HuyaIgnacio Ferrin10 March 2000Trans-Neptunian
QuaoarM. Brown, C. Trujillo4 June 2002Kuiper Belt
ErisM. E. Brown, C. A. Trujillo and D. Rabinowitz 21st October 2003Trans-Neptunian
MakeMakeM. E. Brown, C. A. Trujillo, and D. L. Rabinowitz 31st March 2005Trans-Neptunian

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