Icy ‘Super-Earth’ could be our ninth planet

There is a huge, dark, frozen world lurking on the edge of the solar system, say astronomers. We don’t know what it looks like — or even if it really exists. Could this be Planet X?

Dr Mike Brown still gets angry phone calls in the middle of the night. It has been ten years since he discovered another object orbiting the Sun, a discovery that would eventually lead to Pluto being stripped of its planet status. ‘When all this happened,’ he explained in the New Yorker yesterday, ‘people would say, are there any other planets out there? And I would say, nope, that’s it.’

He was wrong. He and his colleagues at Caltech have discovered ‘strong new evidence’ of a ninth planet ten times the mass of Earth. They first noticed something unusual in the movements of six objects in the Kuiper Belt in 2003. Something massive was affecting their orbits, and one of Brown’s former students suggested that it was a large, elusive planet. Brown set out to prove him wrong; but the more he investigated, the more likely it became.

‘Killing Pluto was fun,’ admits Brown, who even tweets under the handle @PlutoKiller. ‘But this is head and shoulders above everything else.’

If it exists, Planet Nine — or ‘Planet X’ — would follow an ‘elliptical’ orbit, rather than the circular path taken by the other planets. It would take thousands of years to complete a single circuit — but it is still just a theory. Now that they know what to look for, Brown hopes that he or another astronomer will soon spot it through a telescope.

The news, to some, is astonishing. The Hubble Telescope has seen 13.2 billion lightyears into the universe. How can we possibly not know how many planets there are in our own solar system?

And yet there are many things that scientists simply do not know. When Isaac Newton discovered gravity, he became the father of modern physics — and yet no one understands how it works. Meanwhile, 95% of our own ocean remains unexplored; we have no real idea what what lies on the seabed. Scientists are not even sure why we sleep, or how bicycles work.

Know idea

So there are still mysteries left, admit some. But even if it exists, Planet X is so far out of our reach that it is basically irrelevant to our daily life; we know most of the important things back home. In fact we are learning more, and faster, than we ever have before; human knowledge doubles every 12 months; soon it may double every 12 hours. There is hardly a crisis of ignorance.

But this is nonsense, say others. Think about it: we just don’t know how much we don’t know. And that is a good thing; that is what makes the world around us so astonishing, and what makes science such an incredible subject. One day we can just wake up, and a new planet will have made itself known, shifting our perspective of the universe. What could be more wonderful than that?

You Decide

  1. Where should scientists explore next: the ‘ninth planet’ or the bottom of the ocean?
  2. Will we ever know everything there is to know? Would you want to?


  1. As a class, take it in turns to suggest a name for Planet X, and then vote for your favourite. Leave a comment letting us know the result.
  2. Browse through The Day‘s archives to find five other scientific discoveries in the last five years. Rank them in order of importance and explain your reasoning to the class.

Some People Say...

“Knowledge is the most important weapon we can have.”

What do you think?

Q & A

So does Planet X exist, or not?
We still don’t know. Dr Brown says that there is a 68.3% chance: or rather, a ‘frustratingly plausible yet not-assured chance.’
How could we miss something so big?
Because it is very, very far away. Even when it is at its closest point to the Sun, the scientists predict that it would still be 200 to 300 times farther away from the star than Earth. And that’s when it’s closest to us — which only happens every 10,000 years or so. The planet is also surrounded by much brighter lights — Pluto could be 10,000 times brighter. So that makes it very difficult to see, unless you know exactly where to look.
So we may never know? That really is frustrating.
Indeed. But now that the word is out, astronomers all over the world can start looking.

Word Watch

The California Institute of Technology, a prestigious university known for its impressive research into science and engineering.
This is not the same as size or weight; an object’s mass is the measurement of how much physical ‘stuff’ it has.
Kuiper Belt
A region beyond Neptune, in which hundreds of thousands of objects — including Pluto — orbit the Sun.
13.2 billion lightyears
Scientists estimate that the universe is around 13.7 billion years old. This means that the light captured in this picture had been travelling for most of the universe’s life.
Most forces are controlled by their own particles, and yet scientists are yet to discover gravity’s equivalent. And although gravity is believed to be the weakest force, it holds the universe together. How can that be?
There are several theories about why humanity sleeps; none of them have been proven true.
Believe it or not, physicists have not been able to explain exactly what keeps a moving bicycle upright. It just is.
According to a prediction by IBM in 2013.


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