The physicist in search of Planet 9 of the Solar System

The search for Planet Nine at the edge of the Solar System "has just entered in vivo": it is claimed by the young physicist who with Brown demonstrated its existence.

The solar system is a bit different from how it was taught in school until a few years ago. Since Pluto has been downgraded to "dwarf planet", the real planets of the solar system have officially become eight.

Eight planets then, in addition to five dwarf planets and many other minor bodies located essentially between the main asteroid belt and the Kuiper belt are the image of our system as it is recognized by the scientific community.

But evidence is quickly leading a young Russian physicist to the discovery of a new planet at the edge of the Kuiper belt: the solar system's Planet 9.

The "Planet 9" Hypothesis

The hypothesis of the existence of a ninth planet at the edge of the solar system has been around since the beginning of the millennium, but it was first made known in 2016, when The Astronomical Journal published a paper titled "Demonstration of the existence of a distant giant planet in the Solar System."

The article bore the signature of Kostantin Batygin, a very young Moscow-born astrophysicist stationed at Caltech California, as well as the frontman of the rock band Seventh Season and the absolute star of the most "nerdy" channels on YouTube.

Batygin has been working to prove the existence of Planet 9 ever since. It was first hypothesized in 2004 to justify the discovery of the peculiar orbit of the dwarf planet Sedna: exceptionally elongated, and among the most extended in the entire solar system, the orbit of the dwarf planet discovered by Michael E. Brown required new hypotheses.

Officially included in the list of celestial objects that fall under the gravitational influence of Neptune, the story of Sedna has been the focus of speculation that led to the hypothesis of a ninth planet well beyond Neptune, which would be precisely responsible for the particular orbit of the dwarf planet at the edge of the solar system.

In research in 2016, Batygin and Brown, showed that the orbital clusters visible on the Kuiper belt could be maintained in being by a "distant, eccentric, Neptune-type planet."

According to the study, the orbit of this huge planet rests in approximately the same plane as the orbit of the other Kuiper belt objects, and would be able to account for Sedna's strange orbit.

The research "just got into the swing of things"

The orbital groupings observed in the Kuiper belt were not the consequence of observational error or bias. Signed again by Batygin and Brown, the study of 2021 is a fundamental breakthrough in the search for Planet 9.

It is in fact demonstrated here that the gravity of the hypothetical planet is able to "unfreeze" the orbits of the objects inside the Oort Cloud (the first to be recognized as such was precisely Sedna), to put them "in a circle" at the edge of the solar system.

Demonstrating the existence of such a distant planet is no simple matter, and involves extremely complex calculations and concepts, but Batygin's research is quickly putting the data in place.

Planet 9 must have a mass between 5 and 10 times that of Earth, a size sufficient to clear its orbit of larger bodies within 4.5 billion years - exactly the age of the Solar System. That's enough for Planet 9 to be defined for all intents and purposes as a planet in our system, originating in the same way as the eight already known.

According to Batygin and Brown's theory, the ninth planet could be the core of a giant planet ejected from Jupiter's orbit early in the formation of the solar system.

Whatever its origin, Batygin is convinced that we will soon find Planet 9: its existence "naturally explains other, seemingly disconnected, dynamical features of the solar system." As he writes in his much-followed blog, "the search for Planet Nine is just getting underway."