For decades, scientists have theorised there is a ninth planet – what would have been 10th were it not for the downgrade of Pluto to a dwarf planet – in Earth’s neighbourhood. The planet was believed to be 10 times bigger than Earth and 20 times farther out from the Sun than Neptune – the outer-most planet in the solar system – making it difficult for astronomers to spot. However, the Hubble telescope has spotted a planet orbiting so far out from its host star that it adds weight to the Planet Nine theory.
The planet has been called HD106906b and is so big it has roughly 11 times the mass of Jupiter – by far the biggest celestial body in our solar system, excluding the Sun.
Astronomers have been monitoring the planet for 14 years to accurately detect its movements and what it orbits.
Now, the team have found its orbit is so huge it takes an astonishing 15,000 years to complete one trip around its host star, which is more than 330 light-years from Earth.
The planet is so far out from its star that it is more than 730 times the distance between the Earth and the Sun.
The orbit of the planet is also at a slight angle and elongated, influencing the circumstellar disc which surrounds its solar system.
In our solar system, this circumstellar disc is known as the Kuiper Belt.
Meiji Nguyen of the University of California, Berkeley said: “To highlight why this is weird, we can just look at our own Solar System and see that all of the planets lie roughly in the same plane.
“It would be bizarre if, say, Jupiter just happened to be inclined 30 degrees relative to the plane that every other planet orbits in.
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Researchers began believing there was something huge like Planet Nine on the edge of our solar system, as it could explain why the solar system is slightly off balance.
In most star systems, the surrounding planets tend to rotate in line with their host. However, in ours, the planets are at an angle of six degrees off its axis.
Robert De Rosa of the European Southern Observatory in Santiago, Chile, said: “Despite the lack of detection of Planet Nine to date, the orbit of the planet can be inferred based on its effect on the various objects in the outer Solar System.
“This suggests that if a planet was indeed responsible for what we observe in the orbits of trans-Neptunian objects it should have an eccentric orbit inclined relative to the plane of the Solar System.
“This prediction of the orbit of Planet Nine is similar to what we are seeing with HD 106906b.”