Planet Nine: How Could We Miss It?
PLANET 9 It’s four times the size of Earth, only comes along once every 27 million years – and yet it is part of our solar system. Planet Nine may be a rare sight, but it’s an extremely powerful one: when it shows up, it brings with it asteroids that w
The terrifying powers of Planet Nine revealed
Earth has experienced catastrophe after catastrophe. For decades, researchers have been tackling the thorny issue of why, every 27 million years, a mass extinction occurs on our planet. “It’s a strange phenomenon,” explains Professor Daniel Whitmire of the University of Louisiana at Lafayette. “Newer research shows evidence of such events dating as far back as 500 million years.” In research circles, the finger of suspicion points to an undiscovered, ninth planet in our solar system: a phantom that turns up to wreak havoc – namely wiping out life on Earth – and then disappears afterwards. But how could we miss a rogue planet during 5,000 years of astronomical observation? And will Planet Nine spell the end for the human race?
HOW DO YOU FIND AN INVISIBLE PLANET?
The reasons why Planet Nine has wended its merry way for so long without us noticing are simple: “It’s a long way away, reflects little sunlight and moves very slowly around the sun,” explains Austrian astronomer Florian Freistetter. So you can’t really blame scientists for not discovering it. Telescopes around the world have scanned the sky for decades, searching for any abnormalities. And, even if the phantom planet hasn’t been spotted yet, there are obvious clues. If the hunt for who was responsible for these regular mass extinctions was a court case, Planet Nine would have already been sentenced due to overwhelming circumstantial evidence.
The trail leads to the Kuiper belt: a ringshaped cloud of asteroids and dwarf planets, or trans-neptunian objects (TNOS), that previously marked the edge of the solar system. The 13 largest of these celestial bodies are known as extreme trans-neptunian objects (ETNOS) and orbit elliptically around the sun at a distance of roughly 7.5 to 67 billion kilometres. However, the fact that they even exist undermines the long-established laws of physics, giving the hunters of Planet Nine hope: “They’re kind of in a no man’s land,” explains Scott Sheppard, an astronomer at the Carnegie Institution for Science in Washington, D.C. “These objects couldn’t get out there with what we currently know.” No one can explain how they retain their orbits so far away from the sun – unless a huge phantom planet also
“When the solar system was formed, large celestial bodies were flung out from the inner region” Florian Freistetter, Astronomer
drifts through the empty space behind the Kuiper belt, stabilising the 13 outcasts. The regularity of their orbits, all of which are at the same angle to the sun, is also telling. It’s another indication that Planet Nine exists: normally, the gravitational pull of planets such as Saturn or Neptune would disrupt the ETNOS’ route, but that doesn’t happen. In simple terms, this means that, if you take the sun and the eight major planets of the solar system and observe their influence on the 13 ETNOS, the calculations simply don’t add up – at least not without an additional factor. However, if you replace the missing figures in the equation with a ninth planet, orbiting the sun unobserved, the behaviour of the 13 celestial bodies suddenly makes sense. It’s like a puppet show: the researchers can see the puppets dancing on stage and even the strings that move them – and assume there must be something controlling them, even if it’s hidden away. But what does the puppeteer look like?
To construct an astronomical profile of Planet Nine, researchers from the University of Bern drew up a phantom image of the planet. Using computer algorithms, astrophysicists Esther Linder and Christoph Mordasini were able to simulate the properties of Planet Nine, without ever having seen it. “With our study, candidate Planet Nine is now more than a simple point mass; it takes shape, having physical properties,” explains Mordasini. According to their calculations, it’s a gas giant that weights about ten Earths, has a radius of 23,330 kilometres and a temperature of -226°C. Professor Whitmire also created a computer model of Planet Nine and found that the renegade planet is 100 times further away from the sun than the Earth. It’s a crucial clue because the model fits the mass extinction culprit’s profile. Whitmire suggests that it takes Planet Nine exactly 27 million years to orbit the sun, a timescale that coincides with the mass extinctions on Earth. And the sequence of events is clear: every 27 million years, Planet Nine ploughs its way through the Kuiper belt, flinging asteroids towards Earth and resetting life. But the impacts aren’t the worst part: according to researchers, the huge cloud of dust they throw up darkens the sky for years. An encounter with Planet Nine would therefore probably be the end of the road for us. But Professor Whitmire’s theories confirm that we’ve still got a bit of time. The next major mass extinction is not expected to occur for another 16 million years at the earliest.
“We’re becoming increasingly convinced that it does exist” Konstantin Batygin, California Institute of Technology “We are pretty sure there’s a ninth planet out there” MICHAEL BROWN, Astronomer at the California Institute of Technology
OUTER LIMITS Scientists have used computer models to calculate the orbit of Planet Nine. They estimate that it circles our sun at a distance of up to 225 billion kilometres. If correct, it means that the solar system is a lot bigger than previously thoug
PLANET 9 It hasn’t been possible to detect a ninth planet in our solar system yet, but scientists have found evidence of its existence… OBJECTS WITH SUSPECT ORBITS EARTH MASSES ORBIT LENGTH IN EARTH YEARS 1 1 The orbital paths of trans-neptunian objects
EARTH PLANET NINE NEPTUNE