Astronomers Think They’ve Found Evidence for a Ninth Planet Beyond Pluto – And It’s a Giant!

Astronomers now think there’s a ninth planet in the solar system almost certainly. The farthest planet from our Sun is probably a giant, smaller than Neptune but likely larger than the Earth. It is informally called Phattie, but commonly known as Planet Nine.

The new research published in The Astronomical Journal with an article titled Evidence For A Distant Giant Planet In The Solar System. The writers of the article are Caltech (California Institute of Technology) astronomers Konstantin Batygin and Michael E. Brown. Yes, the Same Mike Brown who discovered Eris in 2005 (from images taken on October 21, 2003), the second-biggest dwarf planet (so far) after Pluto.

Mike Brown known as the “Pluto Killer”. In fact, as objects increasingly closer in size to Pluto were discovered in the region, it was already being argued that Pluto should be reclassified as one of the Kuiper belt objects. But the discovery of Eris was the last impact: it led the International Astronomical Union (IAU) to define the term “planet” formally for the first time the following year.Notes 1 This definition excluded Pluto and reclassified it as a member of the new “dwarf planet” category (and specifically as a plutoid).

Ninth Planet, artist's concept
An illustration of what Planet Nine might look like from an artist’s eye. Caltech/R. Hurt (IPAC)

Interestingly, they have had started their research to demonstrate that there’s no ninth planet: it was first proposed in 2014, and it has been the job of Konstantin Batygin and Michael Brown, the scientists in the Division of Geological and Planetary Science at the Caltech, to essentially debunk it. But they reached the exact opposite. Batygin told Nature that “we have a gravitational signature of a giant planet in the outer Solar System”.

The researchers did not observe the planet directly, they merely put together a mathematical model that infers its existence. According to Batygin, they have enough gravitational signature of a giant planet in the outer solar system. The interesting thing is, the scientists claim that some of the most powerful telescopes on Earth probably be capable of spotting it. It can be hiding in some of the photographs taken already by these telescopes and soon be discovered.

Ninth Planet size comparison
Size comparison of the Ninth Planet against the Earth and Neptune. It is smaller than Neptune, but likely bigger than the Earth.
The orbit of the ninth planet
The orbit of the ninth planet. It has 20,000 years of orbital period. It is 60 billion miles from the Sun.

If this ninth planet exists, and probably it does, the researchers suspects it’s 10 times the mass of Earth (for comparison, Neptune has 17 times as much mass compared to the Earth) and 200 times farther from the sun. At that distance, it would take the planet between 10,000 to 20,000 Earth years to complete one trip around the sun. Pluto, for comparison, takes 248 years to complete its orbit. At that distance, the possibility for life is near to none. On the surface (if there is a surface, of course), the Sun will be just a brighter star. The ninth planet is likely a desolate ice ball with a gassy outer layer, like Neptune.

Brown is confident that the ninth planet does exist. He tweeted that “OK, OK, I am now willing to admit: I DO believe that the solar system has nine planets”.

Mike Brown's tweet about the ninth planet
Mike Brown’s (AKA the Pluto Killer) tweet about the ninth planet.

Update: More Evidence Supporting Planet Nine Revealed

Researchers from the University of Madrid published a paper titled “Evidence for a possible bimodal distribution of the nodal distances of the extreme trans-Neptunian objects: Avoiding a trans-Plutonian planet or just plain bias?” which supports the existence of the planet nine. The team studied the nodes for 28 trans-Neptunian objects (ETNOs)Notes 2 and 24 smaller objects, known as Centaurs. Data show that there is a correlation of their orbit: all the nodes appear to be allowed only in a certain range of distances from the Sun. There shouldn’t be any correlation – so, it seems they interact with “something”, like the comets interact with the Jupiter.

The research is in agreement with the original research mentioned above that suggests there’s a massive object beyond Pluto, up to 10 times the mass of the Earth and expected to be about 600 to 700 AU from the Sun.


  1. on August 24, 2006 with an IAU resolution that created an official definition for the term “planet”. According to this resolution, there are three main conditions for an object in the Solar System to be considered a planet:
    1. The object must be in orbit around the Sun.
    2. The object must be massive enough to be rounded by its own gravity. More specifically, its own gravity should pull it into a shape of hydrostatic equilibrium.
    3. It must have cleared the neighborhood around its orbit.

    Pluto fails to meet the third condition, because its mass is only 0.07 times that of the mass of the other objects in its orbit (Earth’s mass, by contrast, is 1.7 million times the remaining mass in its own orbit). The IAU further decided that bodies that, like Pluto, meet criteria 1 and 2 but do not meet criterion 3 would be called dwarf planets. On September 13, 2006, the IAU included Pluto, and Eris and its moon Dysnomia, in their Minor Planet Catalogue, giving them the official minor planet designations “(134340) Pluto”, “(136199) Eris”, and “(136199) Eris I Dysnomia”. Had Pluto been included upon its discovery in 1930, it would have likely been designated 1164, following 1163 Saga, which was discovered a month earlier.

  2. Extreme trans-Neptunian objects (ETNOs) are minor planets in the Solar System that orbits the Sun at a greater average distance with a semi-major axis greater than 150 AU and perihelion greater than 30 AU. The term comes from TNOs, or the Trans-Neptunian objects, minor planet in the Solar System that orbits the Sun at a greater average distance (semi-major axis) than Neptune, 30 astronomical units (AU). 1 AU is the distance between Earth and Sun, which is approximately 150 million kilometres, or 93 million miles.


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