04-05-2025
A strange object 65 billion miles from sun could be the elusive Planet Nine
Just because Pluto was ruled out as a planet in 2006 doesn't mean our solar system only has eight planets. The search for Planet Nine is far from over as scientists continue to uncover clues suggesting something massive may still be lurking in the distant dark beyond Neptune.
Now, a team of international scientists has identified a promising Planet Nine candidate by comparing infrared surveys of the sky taken with a 23-year gap. The object appears to have shifted position over time, just what is expected from a distant planet slowly orbiting the sun.
This is probably the most convincing evidence for Planet Nine so far. It is believed that this planet is five to ten times bigger than Earth and has an orbit wildly different from the known planets.
In 2021, British astronomer Michael Rowan-Robinson combed through old data from NASA's Infrared Astronomical Satellite (IRAS), which scanned the sky in 1983. He spotted a possible Planet Nine candidate with an estimated mass of three to five times that of Earth at around 225 AU from the sun (1 AU is the Earth-sun distance).
However, that object wasn't seen in any other dataset and remains unconfirmed. Recently, Patrick Phan (lead researcher of the current study) and his team took a new approach. They matched IRAS data with images from Japan's AKARI satellite, taken in 2006.
In one IRAS image, they spotted an object. It wasn't in the same place when AKARI later looked, but AKARI did detect an object just 47.4 arcminutes (a bit less than one degree) away, consistent with how far Planet Nine could have drifted in its orbit over 23 years.
This kind of motion is crucial because if something is moving that slowly, it's likely very far away and possibly orbiting the sun. What makes this finding stronger than earlier ones is that it shows up in two different infrared sky surveys—IRAS and AKARI—taken decades apart.
Based on how bright the object appears in both datasets, the researchers estimate it could be even more massive than Neptune. That's surprising because the team was originally looking for something smaller—maybe a super-Earth. Yet, it fits the expectations for Planet Nine's estimated mass and distance better than anything found so far.
Moreover, its suspected orbit is wildly different from the known planets. While Neptune orbits the sun at 30 AU (about 4.5 billion kilometers), Planet Nine might swing between 280 (closest distance from the sun) and 1,120 AU (farthest distance), up to 105 billion kilometers (65 billion miles) away.
That's over 700 times farther than the sun is from Earth. Such a bizarre orbit raises many questions: Did this planet form with the rest of the solar system? Or was it captured from another star long ago?
The possibility of finding a new planet in our own solar system is thrilling. If confirmed, Planet Nine would be the first planet discovered in modern times that wasn't found by accident or by studying close-up orbits.
It would be revealed through indirect evidence, almost like spotting a ghost by the way it moves things around. However, the current study only suggests a possible candidate, and further evidence is needed to confirm its existence.
'The verification of Planet Nine's existence via future observational studies will contribute to our understanding of the evolution and structural dynamics of the solar system,' the study authors note.
Unfortunately, NASA's more recent WISE (Wide-field Infrared Survey Explorer) sky surveys didn't pick up this object, but Phan suggests that this might be because the planet has moved from its 2006 position. Without knowing its exact orbit, it's impossible to say where it is now.
He is hopeful that future observations will validate the findings from his research.
The study will soon be published in the journal Publications of the Astronomical Society of Australia.
