Is it Planet 9, is it Planet X, or Both?

As a species we human beings are rather obsessed with the end of our world and how that is going to happen. From zombie apocalypses to giant asteroids hitting the Earth, we’ve pretty much thought of everything. However there is a new idea in town, and it makes giant asteroids look like pebbles.


Here you can see the hypothesised orbit of Planet 9 along with some other Kupier Belt Object (KBOs) including Sedna. At the centre of the image you can see the Sun and you can see just how far away it is. The other planets in our solar system are not visible. Credit Caltech/R. Hurt (IPAC)

Here you can see the hypothesised orbit of Planet 9 along with some other Kupier Belt Object (KBOs) including Sedna. At the centre of the image you can see the Sun and you can see just how far away it is. The other planets in our Solar System are not visible. (Image Credit Caltech/R. Hurt (IPAC))


You may be familiar with something called Planet 9 or Planet X. Back in January 2016 a paper was published in the Astronomical Journal claiming that astronomers Konstantin Batygin and Mike Brown had found evidence of a Neptune-sized planet beyond Pluto. They estimate the hypothetical world to have a highly elliptical orbit with a period of 15 000 years or so in and has a mass ten times that of the Earth. Brown has asserted that this planet is most likely an ejected ice giant planet with a similar composition to that of Uranus and Neptune. Brown first thought ‘Planet X’ existed after his discovery of Sedna, a KBO and possible dwarf planet that orbits the Sun at an impressive 76 AU, beyond Neptune.  Brown sees observations of a population of sednoids such as V774104 with similar orbits  as compelling evidence of a large distant planet in the outer reaches of the Solar System. To try to prove the existence of this ice giant, Batygin and Brown intend to use mathematical modelling and computer simulations to make the find. This all sounds tremendously impressive, and it is, but there has actually been no direct observation of the planet yet. You will read in several articles online that there is a “newfound planet”, please remember that it is only a hypothesised planet, and we only think that it is there.

Even though Planet 9 is a hypothesised planet with a highly elliptical orbit, people are taking a great interest in it. In fact, researchers at the University of Bern have created a model of what the mysterious ice giant would look like. In a paper that was published in Astronomy & Astrophysics they state that a planet like Planet 9 would be roughly 47 K (-226 °C). The atmosphere would be made up of hydrogen and helium, and underneath would be a gas layer of the same composition. You’re probably thinking, “Hold on a minute! What is the difference between an atmosphere and a gas layer? Aren’t they just the same thing?” An atmosphere is a layer of gases surrounding a planet or other material body, which is held in place by the gravity of that body. An atmosphere is more likely to be retained if its gravity is high and the atmosphere’s temperature is low. Gas Giants differ greatly from the rocky planets. The rocky planets have hard surfaces but with gas giants, the further down into the planet you go the dense the gas becomes. So the gas layer of a gas giant would be a layer that consists of the same gas as the atmosphere, with maybe a few extras added in here and there, but it is much denser. Underneath the gas layer would be ice (in this context water, methane, and ammonia in the form of a hot, high pressure fluid) , and then beneath that a silicate (MgSiO3) mantle. Finally they state that Planet 9 would have an iron core unlike the other gas giants in our Solar System, which are hypothesised to have rocky cores, or in the case of Jupiter a core that is more likely to be slushy with a consistency that is not quite solid or liquid.


This is the hypothesised make up of Planet 9 as created by the astronomers at the University of Bern. You can very clearly see the different layers and their makeup. Credit E. Linder, C Mordasini and the University of Bern.

“Soft and creamy on the outside with a crunchy centre” This is the hypothesised make up of Planet 9 as created by the astronomers at the University of Bern. You can very clearly see the different layers and their makeup. Only astronomers could call a 2000 degree fluid “ice”. (Image Credit E. Linder, C Mordasini and the University of Bern.)


The University of Bern scientists have also said in regards to the discovery of the planet that future telescopes like the Large Synoptic Survey Telescope under construction near Cerro Tololo in Chile or other dedicated surveys should be able to find or dismiss the existence of Planet 9. Let’s hope that if they do find and prove Planet 9’s existence that the naming of the planet doesn’t come down to the general populous of Earth, or else we could end up with a planet named Planet McPlanetFace.

So where does the end of our world come in to all of this? How have we managed to turn a hypothetical planet into an earth shattering destroyer (literally)? This is where the “Nibiru Cataclysm” comes in. Some of you might be familiar with this, but if you’re not here is an explanation.

The Nibiru cataclysm is an idea that has been orbiting through the furthest, darkest and weirdest corners of the internet since the early 1990s and is said to be a supposed disastrous future encounter between the Earth and a large planetary object. This apocalyptic encounter would either be a near miss, or even an actual collision. Few astronomers who have heard of this omen of doom, those who have find the idea absurd. It is believed (by the sort of folk who believe in this sort of thing) that this event will happen in the early 21st century. Convenient. The perpetrator behind this apocalyptic event? An object that has often been referred to as Planet X or Nibiru.

Nibiru is a word taken from the extinct Akkadian language used in ancient Mesopotamia, which translates into “crossing,” or “point of transition.” In Babylonian astronomy, Nibiru is also a term for the equinox and its associated astronomical objects. Nibiru is also linked to well-known pseudoscientific author Zecharia Sitchin (1920-2010). He was a Russian-born American author of books who proposed an explanation for human origins involving ancient astronauts. This was based on Sitchin’s personal interpretations of ancient writings; genuine scholars of these texts completely disagree with Sitchin’s claims. In his book The 12th Planet (published 1976) Sitchin attributes the creation of the ancient Sumerian culture to the Anunnaki, which he states was a race of malign extra-terrestrial beings from a planet beyond Neptune called Nibiru. He believed this hypothetical planet of Nibiru to be in an elongated, elliptical orbit in the Earth’s own Solar System. Sounds familiar doesn’t it? Sitchin held the belief that Nibiru came into the inner Solar System every 3600 years and when it did, the odious  Anunnaki set off in spaceships to destroy or pillage other planets. Sitchin’s books allege that the Anunnaki are particularly interested by Earth because they covet our planet’s reserves of gold, so we ought to expect a looting expedition from Nibiru on its next passage by the Sun.

This foolishness all sounds like some 1930s Flash Gordon style pulp sci-fi story but it has been widely imitated and popularised by crackpots and charlatans for the past twenty years. Many of these people have set very specific dates for Nibiru returning to destroy civilisation on Earth. Nibiru was said to be about to come back in 2003, 2010, 2011, 2012 and “soon” (its approach is apparently being covered up by NASA and its sect of dastardly astronomers). Sadly some people have completely bought into this sad belief, panicking (allegedly in one case killing a pet dog to prevent its suffering) or exulting in the impending doomsday. However Sitchin’s Nibiru is an impossible entity. If it were real we would have seen some evidence in the orbits of the others planets.

Is there a difference between Nibiru and Planet X? Some people are confusing them, and goodness knows you don’t want to confuse the theories that could lead to your inevitable doom. As discussed, Nibiru is said to be a planet with an orbit of roughly 3,600 years on a never ending, our end is neigh, collision for the Earth. Planet X on the other hand is said to be a brown dwarf. A brown dwarf is a substellar object not massive enough to sustain fusion reactions in their cores, like main-sequence stars. When it comes to mass, brown dwarfs are between the heaviest gas giants and the lightest stars. This is where the Nemesis model comes in and is something that is used to try and explain mass extinctions. The discovery of an apparent 26 million year period in mass extinctions by David Raup and John Sepkoski (Periodicity of extinctions in the geologic past – published 1984) invited the proposal of three astronomical models. The Nemesis model hypothesised that the extinction period was associated with comet showers that were triggered when a solar companion object (such as a brown dwarf or even a very small red dwarf star) in an eccentric orbit scattered comets when passing through its perihelion point located in the inner Oort Cloud. This intriguing idea got a lot of attention in the ’80s, even inspiring Isaac Asimov to write a tie-in novel Nemesis in 1989.

The Planet X model is very similar to the Nemesis model except it talks about a trans-Neptunian planet. The planet’s perihelion and aphelion points pass through the ecliptic plane twice during each circulation period, triggering comet showers. We won’t go into the third astronomical model as it has been challenged on the basis of inconsistency with the 26 million year period.


A Diagram showing the distance of the Oort Cloud from the Sun. The Oort Cloud is estimated to be between 5,000 and 50-100,000 AU away. Credit NASA

A diagram showing the distance of the Oort Cloud from the Sun. Don’t be fooled into thinking Alpha Centauri is just past the edge of the Oort Cloud, the distance scale in Astronomical Units is logarithmic: the Oort Cloud is estimated to be between 5000 and 50-100 000 au away, Alpha Centauri is 278 000 au.  (Image Credit NASA)


In these two models that talk about a solar companion or a trans-Neptunian planet, at no point do they say that these objects are making a direct line for Earth for a disastrous collision. The only thing these models suggest is that these objects would cause comets showers that came from the Oort Cloud and even then, this is all theory. In both of these models it is stated that the objects are trans-Neptunian, or lurking somewhere in the Oort Cloud. The Oort cloud is an estimated 5000 to 50,000 AU away. That’s pretty far, especially when you consider that 1 AU is the distance between the Earth and the Sun. Comets that lurk in the Oort Cloud are called long term comets and can take millions of years to orbit the Sun. Are you getting what I’m trying to say here? Anything trans-Neptunian, especially the Oort cloud is really far away and if something was coming towards the Earth from there, it would take a very long time to get here. I have no idea who would ever dream of stating that a planet or some other solar object is hurtling its way towards to Earth for a fatal collision. Someone who has watched too many disaster movies maybe?

Back to Planet 9. Before we all start to fear for our lives at this horrifying prospect of a hypothesised planet (forgetting about Nibiru and Planet X) crashing into, or just missing our own, let’s look at the science of it first.


The Late Heavy Bombardment was probably very similar to the "comet storm" (artist's impression shown) currently being experienced in the Eta Corvi system 59 light years from the Sun. (Image credit: NASA/JPL-Caltech)

The Late Heavy Bombardment was probably very similar to the “comet storm” (artist’s impression shown) currently being experienced in the Eta Corvi system 59 light years from the Sun. (Image credit: NASA/JPL-Caltech)


I want to start by looking at something called the Grand Tack theory. It is a theory that suggests that Jupiter started to form a lot closer to the Sun and then gradually travelled outwards to the position it is in now. This can show us a gas giant planet that wasn’t yet set in its orbit and travelled the solar system. Once it got further out, there was some interplay between Jupiter and Saturn and then we come into the Late Heavy Bombardment (LHB). The LHB occurred roughly 4.1 to 3.8 billion years ago and was a period where there was a lot of heavy comet and asteroid bombardment of the planets, including the Earth. Many of the craters that can be found on the Moon and other bodies within the Solar System record this event. In fact the LHB could also be called the Lunar Cataclysm, and through studies of the craters on the Moon’s surface over the years, the analysis has been able support the hypothesis that a brief pulse of impacting objects 4 billion years ago was due to gravitational disturbances caused by the reorganization of the giant planets as their orbits changed. The collisions with the Earth have long since been erased due to the movement of the tectonic plates, however it is theorised that the comets that hit the Earth during the LHB provided our planet with its water. Any life that was present or emerging on Earth at this time would have been in continual peril of being blasted out of existence. It is possible that life emerged only after the bombardments began to decrease. If it began earlier, life on Earth might have been disrupted or even restarted by this relentless bombardment. All modern life may have evolved from a second genesis!

After the bombardment, things began to settle down in the Solar System. The planets became settled within their orbits and they have been pretty regular in their orbits since. Nothing has wandered since then, and we’re not being bashed about by huge comets or asteroids. With this in mind, you would imagine the same for Planet 9. It is predicted to be further out from Neptune, so how could the planet suddenly change within its set orbit and move in close enough to make impact with the Earth? That’s a long way to travel for a hypothetical planet. Why hasn’t the same been said about Jupiter, a planet that in theory has already travelled around within the Solar System?


 Image Credit: NASA/JPL/Space Science Institute

Giant Jupiter has been in a stable orbit for billions of years. (Image Credit: NASA/JPL/Space Science Institute)


You don’t hear any doomsday threats about Jupiter suddenly hopping out of its orbit and making its way towards the Earth. Why do people think they can get away with the same when it comes to a planet that has yet to be discovered? It sounds an awful lot like scaremongering if you ask me. When you look at the balance of gravitational force and centripetal force we call an orbit it also gives a pretty good reason as to why nothing has moved from its course.


The Sun is at the centre of the solar system and is the domiant force that dictates the orbits of the planets. The Sun is 6000 degrees Celceus on its surface and 14,000,000,000 degrees Celsius at its core. Credit NASA/SDO

The Sun is at the centre of the solar system and is the dominant force that dictates the orbits of the planets. The Sun is 6000 degrees Celsius on its surface and 14,000,000,000 degrees Celsius at its core. Credit NASA/SDO


The Sun is the largest body in the Solar System and dominates it. It contains more than 99% of the mass of the Solar System. The Sun’s central mass applies the greatest gravitational force in the solar system and holds all the other objects in orbit and dictates their motion. The planets travel around the Sun in orbits called ellipses. An ellipse is basically a slightly squashed circle. When an object moves in a circle its speed remains constant but as the direction is constantly changing so is its velocity. This is because velocity has both size and direction whereas speed only has size. For an object moving in a circle a force is required to change the direction as defined by Newton’s first law of motion. This force constantly pulls the object towards the centre of the circle. A force that pulls an object towards the centre of a circle is called centripetal force. The source for the centripetal force in the solar system is the gravitational force of the sun. Without the centripetal force from the sun the planets would travel in a straight line. The velocity of the planets is high enough so that they continuously accelerate towards the Sun without ever leaving their orbits. It is for this reason that the planets do not fall into the Sun from its strong gravitational force of attraction.

To sum it up, the Sun is the thing that is keeping the planets in their orbits, and why nothing has really changed in a while. This will be the same for the hypothetical Planet 9. The Sun would be dictating its orbit along with the other planets, and so it could not fall out of its orbit beyond Neptune and come hurtling towards us, unless something happens to the Sun, and we all know nothing major is going to happen with to it for a long time. Planet 9 (which may not even exist) is not the same as the crackpots’ Nibiru or concept of Planet X and probably not the same as astronomers’ hypothesised Nemesis.

The main thing to take from this article is to not worry about some hypothetical planet coming towards us to end it all, whether it be “soon” or in the years to come that will undoubtedly be “predicted” by some scaremongering doomsday preacher. Yes be excited that there could be a new planet out there, be happy if it is actually discovered, but don’t worry about it crashing into the Earth. If it is found, it will be far too far away for us to even see in the night sky with the unaided eye. If it is discovered it may have a different orbit to all of the other planets, but it will most likely be settled comfortably in that orbit, and not jumping out of it for some random reason as its great overlord (the Sun) will be keeping it in its place. You don’t see the other gas giants doing that, they know how to follow orders. It is simply the fact that it hasn’t been found yet, and is still only there in theory that people are blowing it all out of proportion. When you can’t see something or understand it, that’s when it becomes scary. Could we maybe think of Planet 9 as a ghost planet? No I think that might cause even more problems. By keeping your mind open, and doing your research through scientific websites and journals, you can reassure yourself that nothing untoward is coming our way.

(article by Heather Taylor, Education Support Officer)


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