If you’ve been having trouble remembering how many planets are in the solar system after Pluto’s unceremonious demotion, get ready to revise your understanding of the universe again. According to the calculations of scientists at the Complutense University of Madrid (UCM, Spain) and the University of Cambridge (United Kingdom) not only one, but at least two planets must exist to explain the orbital behaviour of extreme trans-Neptunian objects (ETNO)
The most accepted theory states that the orbits of ETNOs should be distributed randomly. And yet what is observed is completely different; obviously, something must be influencing their orbits.
“This excess of objects with unexpected orbital parameters makes us 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,” said Carlos de la Fuente Marcos, one of the researchers, in a news release.
“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.”
The researchers analysed the Kozai mechanism, related to how a large body’s gravity is exerted on the orbit of another smaller and much further away object.
They used the experience of comet 96P/Machholz1, under the influence of Jupiter, as a reference. Their numerical calculations seem to support their hypothesis.
Despite their surprising results, the authors recognise that their data comes up against two problems. On the one hand, their proposal goes against the predictions of current models on the formation of the solar system, which state that there are no other planets moving in circular orbits beyond Neptune.
However, the recent discovery by the ALMA radio telescope of a planet-forming disk more than 100 astronomical units from the star HL Tauri, which is younger than the Sun and more massive, suggests that planets can form several hundred astronomical units away from the centre of the system.
On the other hand, the team recognises that the analysis is based on a sample with few objects (specifically 13), but they point out that in the coming months more results are going to be published, making the sample larger. “If it is confirmed, our results may be truly revolutionary for astronomy,” says de la Fuente Marcos.
Last year two researchers from the United States discovered a dwarf planet called 2012 VP113 in the Oort cloud, just beyond our Solar System. The discoverers consider that its orbit is influenced by the possible presence of a dark and icy super-Earth, up to ten times larger than our planet.
Bottom Line: The Kuiper Belt, spanning 4.5 to 7.4 billion kilometres, holds trillions of objects which are remnants of the early solar system. Even beyond lies the spherical Oort cloud from where many comets originate.