Two 'unknown planets' may lie hidden beyond Pluto

A recent study has revealed that there may be at least two unknown planets hidden well beyond Pluto.

According to the calculations of researchers at the Complutense University of Madrid and the University of Cambridge, not only one, but at least two planets must exist to explain the orbital behaviour of extreme trans-Neptunian objects (ETNO), whose gravitational influence determines the orbits and strange distribution of objects observed beyond Neptune.

The most accepted theory establishes that the orbits of these objects, which travel beyond Neptune, should be distributed randomly, and by an observational bias, their paths must fulfill a series of characteristics: have a semi-major axis with a value close to 150 AU (astronomical units or times the distance between the Earth and the Sun), an inclination of almost 0 degree and an argument or angle of perihelion (closest point of the orbit to our Sun) also close to 0 or 180 degrees.

Co-author Carlos de la Fuente Marcos explained that this excess of objects with unexpected orbital parameters makes them believe that some invisible forces are altering the distribution of the orbital elements of the ETNO and we consider that the most probable explanation is that other unknown planets exist beyond Neptune and Pluto. "The exact number is uncertain, given that the data that we have is limited, but our calculations suggest that there are at least two planets, and probably more, within the confines of our solar system," adds the astrophysicist.

To carry out the study, the researchers have analysed the effects of the so-called 'Kozai mechanism', related to the gravitational perturbation that a large body exerts on the orbit of another much smaller and further away object.

The study is published in the journal Monthly Notices of the Royal Astronomical Society Letters.