For those of you that are still bearing the psychological scars from Pluto’s demotion from planet to dwarf planet a decade ago, here is news that may add salt to the wounds. Published recently in the Astronomical Journal, Konstantin Batygin and Mike Brown claim they have found evidence of a Neptune-sized planet beyond Pluto. It’s estimated to orbit the Sun every 15 000 years or so in a highly elliptical orbit and to have a mass ten times that of the Earth. At 20 times or more the distance of Neptune from the Sun on average, it this hypothetical world (and its moons) would be very cold and dark.

Batygin and Brown suggest the planet’s existence through mathematical modelling and simulations with detailed analyses of other distant objects and their strange orbital features. Both are confident that this time they have found the so-called ‘Planet X’ yet they haven’t been able to see it.

Artist's impression of Planet Nine as an ice giant eclipsing the central Milky Way, with a star-like Sun in the distance. Neptune's orbit is shown as a small ellipse around the Sun. (Image credit: Tomruen, nagualdesign CC BY-SA 4.0 )

Artist’s impression of Planet Nine as an ice giant eclipsing the central Milky Way, with a star-like Sun in the distance. Neptune’s orbit is shown as a small ellipse around the Sun. (Image credit: Tomruen, nagualdesign CC BY-SA 4.0 )


This is not necessarily a new theory as for many years it was thought that a fifth gas planet could have been ejected from the early Solar System, 4. 5 billion years ago due to a gravitational encounter with Jupiter and Saturn, for example during the period described by the Nice Model. Slowed by gas drifting around the young Sun, the planet could have settled into the elliptical orbit it is hoped to still be in today. Therefore this only further supports the evidence that Planet Nine could exist.


Planet Nine may closed resemble Neptune as seen from Voyager 2 (Image credit: NASA)

Planet Nine may closed resemble Neptune as seen from Voyager 2 (Image credit: NASA)

In the early 19th century Uranus’ apparently strange orbit led scientists to believe another planet existed leading directly to the discovery of Neptune. By 1906 Percival Lowell had begun his search for the Trans-Neptunian planet, ‘Planet X’, at his observatory in Flagstaff, Arizona. In 1930 Pluto was discovered by Clyde Tombaugh but after a while it became clear that its small size meant it couldn’t influence the orbit of Uranus or Neptune. Tomabaugh had just been lucky! Later when Voyager 1 and Voyager 2 flew past Uranus and Neptune it was decided the unusual orbits was a characteristic of flows inside the planets rather than an outside gravitational force. Despite this finding, the search for ‘Planet X’ continued.
In 1990 it was suggested that a Jupiter-sized planet lurked on the outskirts of the Solar System and was the cause of many stray comets. Even towards the end of 2015 scientists at the European Southern Observatory in Chile put forward their results obtained from the Atacama Large Millimetre/Submillimetre Array (ALMA), a large group of telescopes stating that they had found a large object on the edge of our solar system, the proposed ‘Planet X’. In a second report it was proposed this new object is close to the binary star Alpha Centauri and could be an Earth like planet beyond Pluto. However Mike Brown of Caltech said ‘The logical leaps are astounding. What they really saw is a little blip and then six months later another little blip.’ He also remains sceptical for the reason that ALMA‘s field of view would make finding an object like this incredibly difficult, yet the search for ‘Planet X’ continues.


Orbital correlations among six distant trans-Neptunian objects led to the hypothesis (Image credit: nagualdesign CC0)

Orbital correlations among six distant trans-Neptunian objects led to the hypothesis (Image credit: nagualdesign CC0)

Mike Brown first thought ‘Planet X’ existed after discovering Sedna, a possible dwarf planet that orbits the Sun at an average distance of 76AU, far beyond Neptune. Its strange orbit left Brown thinking that something significantly large existed beyond Neptune as Sedna was too far away to be gravitationally disturbed by Neptune. This didn’t necessarily have to be a planet, as a star or stellar nursery would have been nearby at the time of the solar system’s creation which could have affected Sedna’s orbit. From this period, many other smaller icy objects such as V774104  and 2012 VP113) have been discovered and scientists, Scott Shepherd and Chad Trujillo looked at the unusual clumping of these distant objects. They even went as far as to suggest a large planet existed beyond Neptune that distorts the orbits of these objects but they never took their research any further. Batygin and Brown began discussing the results and plotting the orbits of these distant objects. They noticed something odd in their orbits, not only did all objects come very close to the Solar System at perihelion but their position was clustered. By inserting different sized planets into the diagram, Brown and Batygin settled on a favoured size, between 5 and 15 Earth masses, this also meant its orbit was best suited anti-aligned so it was opposite to the smaller objects perihelion. Therefore these objects would cross ‘Planet X’s’ orbit but not when it is nearby.
Many scientists are split in their views of Planet Nine’s existence, planetary dynamicist Alessandro Morbidelli says that he is ‘quite convinced by the existence of a distant planet’ as Brown and Batygin have made a ‘solid argument’ for Planet Nine, whereas planetary scientist Dan Jewitt who was behind the discovery of the Kuiper Belt remains sceptical as the 0.007% claim that the icy objects positions are coincidental is in astronomical terms 3.8 sigma. Confidence in this statistical significance has been misplaced in the past, and Jewitt worries many previous discoveries around the 3 sigma threshold have been wrong before.
Another problem arises with NASA’s Widefield Infrared Survey Explorer (WISE) which could potentially rule out the existence of planet nine. WISE completed a survey of the sky looking for the heat of brown dwarfs and Saturn- sized or larger planets as far our as 10 000 AU, according to a study by Kevin Luhman, an astronomer at Pennsylvania State University in 2013. However Luhman states that if planet nine is Neptune sized or smaller it could have been missed. Another survey was conducted for 20% of the sky, sensitive to cooler radiation and Luhman is now analysing this data in case it was detected then and overlooked.
At this stage I think it is a good theory and one the science community will be intrigued to see appearing but for many it may be the case of ‘seeing is believing’. Many telescopes have a small field of view taking into consideration the sheer size of the night’s sky. However one telescope has already been suggested for spotting ‘Planet X.’ The Subaru is an 8 metre Japanese telescope in Hawaii which has a huge field of few and has enough light to detect faint objects. The Subaru allows scientists to scan large parts of the sky every night although Brown says it could take up to 5 years to scan some of the area where ‘Planet X’ is suspected.
It’s unclear how long it will take to prove Planet X’s existence but it will no doubt be a huge discovery if found and what should it be called? Following traditional naming shall it be after a Greek or Roman god, or after those who discovered it or maybe something completely different? Leave your suggestions in the Comments section below.

Please note:

  • If Planet Nine really exists, it is certain that it has never and will never come close to the inner Solar System planets including Earth.
  • It is not linked to any mythological or real disaster.
  • It is not and was not known as “Nibiru”
  • It was not known to, observed or recorded by the Sumerians, Mayans or any other ancient or historical near Eastern or Meso-American civilisation.


(Article by Samantha Steed, Education Support Officer)


Angelus · March 27, 2016 at 19:17

I want is named Ragnar

William F. Maddock · March 25, 2016 at 16:09

Tobe Ra’ah

It is exotic, just like Planet 9 is, if confirmed, and it means what this planet would be showing itself as: Good Shepherd.

Mark S · March 4, 2016 at 19:20

Artemis, Goddess of the Hunt. People have been hunting for this planet for a long time.

bid · March 3, 2016 at 13:10

Wasn’t there a wandering red dwarf, that “touched” the Oort cloud 70.000 years ago, or did that calculation turn out to be wrong? I wonder how strong occurrences like that can influence the orbits of the outer dwarf-planets.

admin · March 2, 2016 at 10:34


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[…] 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 […]

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