Researchers think they may have discovered a giant planet on the outer reaches of the solar system.
The potential new planet, nicknamed Planet 9, is thought have a mass 10 times that of Earth, and could take between 10,000 and 20,000 years to orbit the sun.
One of the researchers at the California Institute of Technology who discovered the object's existence happens to have played a key part in the demotion of Pluto, which was previously classed as the Solar System's ninth planet.
Along with Konstantin Batygin, the professor of Planetary Astronomy Mike Brown believes he may have discovered a real ninth planet to replace Pluto.
'The most planet-y of planets'
At 5,000 times the mass of Pluto, the professor says there should be no debate about Planet Nine's status as a true planet, calling it "the most planet-y of the planets in the whole solar system."
Konstantin Batygin added that for the first time in over 150 years there is solid evidence that the solar system's planetary census could be incomplete.
Discovery of 'Planet Nine'
The scientists inferred Planet Nine's existence from the gravitational influence it was having on objects with unusual orbits in the Kuiper Belt - the ring of rocky bodies surrounding Neptune.
On average it is 20 times further from the sun than Neptune - the furthest planet from the sun in our solar system - which orbits at a distance of 2.8 billion miles.
The team and their colleagues have begun searching the skies for Planet Nine, but do not currently know its supposed whereabouts.
Brown has urged others to get involved in the search saying he "would love to find it" but they published their findings in the hope that "other people are going to get inspired and start searching".