A gravitational mystery at the doors of the solar system
It all started in 2016, when two Caltech astrophysicists, Mike Brown and Konstantin Batygin, note a disturbing phenomenon: several icy bodies of the Kuiper belt-an area beyond Neptune-seem to be improbably aligned. A bit as if something, massive and invisible, disrupted their trajectory.
A signal from the past
To unravel this mystery, a team led by Terry Phan, doctoral student at the National University Tsing Hua (Taiwan), turned to the archives. Rather than waiting for an ultra-modern telescope to the benchmark by chance, the researchers analyzed the infrared data of two former satellites: IRAS (launched in 1983) and Akari (2006-2011).
And there, surprise: a bright, discreet but consistent point, appears in the two databases, exactly with the same coordinates. This point moves slowly, as you would expect a massive object located very far from the sun. Too slow for an asteroid, too clear to be a simple instrumental artifact. What awaken the interest of the community.
The signal, published at the end of April 2024 on the Arxiv prepublications platform, was considered serious enough to be accepted in a scientific journal with a reading committee: Publications of the Astronomical Society of Australia.
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False track or major discovery?
But should we scream victory? Not so fast. Mike Brown, one of the initiators of the planet Neuf hypothesis, was skeptical. According to its calculations, the apparent movement of the infrared point detected by Phan has a 120 ° orbital inclinationfar beyond that he provided (about 20 °). Clearly: this object, if exists, would move against the rest of the solar system. This would make it very atypical, even downright incompatible with the planet 9 model.
“” This is probably not our famous planet ”, He told Science magazine. “But that could well be another unknown planet … And that would already be huge. »»
This remark says a lot: even if this signal does not correspond to the initial expectations, it is not excluded that it is still a new celestial object. Perhaps a dwarf planet, perhaps an intruder from another system. The unknown remains whole, but scientific interest is undeniable.
The decisive year: 2025
To be clear, all eyes turn to the southern hemisphere, where the Vera C. Rubin telescope enters its last phase of preparation. Equipped with the largest digital camera ever built, this observation monster will systematically sweep the southern sky as soon as it entered service.
This telescope was thought, among other things, for this kind of mission: to identify weakly luminous objects, moving slowly, in the remote regions of the solar system. With its unrivaled resolution and its ability to accumulate in -depth images, Vera Rubin could identify – or exclude – the presence of the new planet in the next two years.
What if planet 9 didn't exist?
Of course, there remains a possibility that many scientists no longer spread: what if planet 9 was just a mathematical mirage? A statistical illusion caused by observation or a poorly understood gravitational effect? After all, other explanations to strange orbits of transneptunian objects have been proposed, ranging from the fragmentation of ancient massive bodies to collective interactions between frozen objects.
But even if this ghost planet were never confirmed, the quest itself would have nothing useless. It pushes scientists to search the archives, to relying gravitational models, to design new instruments, to think differently.
A border hunt for the known
Whether we discover it or not, the planet 9 embodies something fundamental in the scientific approach: the ability to question the invisible, to follow a tenuous track over millions of kilometers, to explore the margins of what we thought we knew.
What if this mysterious infrared point, spotted in archive dust, turned out to be something else? An unknown planet, a forgotten fragment of the solar system, or an interstellar visitor? The year 2025 may well provide us with an answer. Or a new mystery.
