There could be an Earth-like planet hiding in the Kuiper Belt

Far past the reaches of Neptune, two scientists suggest there could be a planet hiding in our Solar System.

This planet is not the hypothesised giant ‘Planet Nine’ far further flung, but instead an Earth-sized planet on a tilted orbit.

“We predict the existence of an Earth-like planet and several trans-Neptunian objects on peculiar orbits in the outer Solar System which can serve as observationally testable signatures of the putative planet’s perturbations,” the team write in their new paper.

The scientists – Patryk Sofia Lykawka of Kindai University in Japan and Takashi Ito of the National Astronomical Observatory of Japan – have investigated trans-Neptunian objects (TNOs) and weird clustering behaviour.

The two authors have published their paper in The Astronomical Journal.  

Past Neptune at around 30 astronomical units sits the Kuiper belt, a group of icy rocks and dwarf planets, including Pluto, Quaoar, Orcus and Makemake.

While Pluto was once a planet, it’s worth noting that dwarf planets are small. Pluto, which is the biggest, is just 18% the size of Earth, smaller than Earth’s Moon.

This new planet on the other hand (if it indeed exists) would be 1.5-3 times the size of Earth.

Looking at the way the TNOs cluster, the team also suggested that the planet could be between 200 and 500 astronomical units (AU) away from the Sun and tilted about 30 degrees. For reference, Pluto is 39 AU’s from Earth.

There’s plenty left to do before we can confirm that this truly is a planet. The scientists would have to find it for starters.

But this might not be as hard as it might first seem. The researchers have already suggested what they can do to find out more. Because the planet’s gravity would cluster the TNOs in particular definable ways, it should be possible to analyse these TNOs to discover if this hidden planet really does exist.

“In conclusion, the results of the Kuiper Belt planet scenario support the existence of a yet-undiscovered planet in the far outer Solar System,” the team write.

“More detailed knowledge of the orbital structure in the distant Kuiper Belt can reveal or rule out the existence of any hypothetical planet in the outer Solar System.”

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