Spanish researchers conducting a study on the furthest objects in the Solar System have uncovered new evidence to support the existence of an undiscovered massive distant planet in the Solar System.

It has been dubbed Planet Nine and the first piece of evidence was how the orbits of trans-Neptunian objects (TNOs) are all distributed in certain directions. This was proposed by researchers at Caltech in January 2016 and several new pieces of evidence have been added since then. Another group of researchers working on TNOs detected some observational biases in their own work and suggested that the Planet Nine evidence based on TNOs needed to be checked again.

In a paper, published in the Monthly Notices of the Royal Astronomical Society: Letters, researchers from the University of Madrid have used a new technique to study some of the most distant objects in the Solar System, aptly named extreme trans-Neptunian objects (ETNOs).

ETNOs are at least 150 times further from the Sun than the Earth (150 Astronomical Units, 1 AU = distance from Earth to Sun) and they don’t cross Neptune’s orbit. The team performed the best measurement to date of the nodes of the ETNOs. The nodes are the two points where the orbit of a celestial body crosses the plane of the Solar System. The nodes' position mainly depends on the size and shape of the orbit, which makes them quite free from observation bias.

The team studied the nodes for 28 ETNOs and 24 smaller objects, known as Centaurs. They saw that all the nodes appear to be allowed only in a certain range of distances from the Sun and it they all appear to correlate, and there shouldn’t be any correlation.

"Assuming that the ETNOs are dynamically similar to the comets that interact with Jupiter, we interpret these results as signs of the presence of a planet that is actively interacting with them in a range of distances from 300 to 400 AU," co-author Carlos de la Fuente Marcos said in a statement. "We believe that what we are seeing here cannot be attributed to the presence of observational bias."

The research is in agreement with the original research that suggests there’s a massive object there, up to 10 times the mass of the Earth and expected to be about 600 to 700 AU from the Sun. The researchers will now look at the finding new evidence for the existence of Planet Ten a Mars-size object that should be located much closer, only 50 AU away.