Decades of Searching May Finally Pay Off: Planet Nine Candidate Found

The elusive Planet Nine has captured the imagination of astronomers and the public alike for nearly a decade. While its existence remains theoretical, a newly published study offers the most promising hint yet that this hidden world might truly be out there. Using decades-old infrared space telescope data, researchers have identified a strong candidate that could finally point us to the mysterious giant lurking beyond Neptune.

The Strategy Behind the Search: Mining the Infrared Archives

Finding a faint, distant planet like Planet Nine requires more than just powerful telescopes; it demands clever strategies. Researchers led by Terry Long Phan turned to two important infrared surveys: IRAS (Infrared Astronomical Satellite, 1983) and AKARI (a Japanese infrared observatory, 2006). By comparing the two datasets separated by 23 years, they hoped to spot faint objects moving slowly across the sky — precisely what would be expected from a massive planet orbiting hundreds of astronomical units (AU) away.

The technique focused on analyzing AKARI’s Far-Infrared Monthly Unconfirmed Source List (AKARI-MUSL), a catalog better suited for catching faint moving objects than traditional surveys. Researchers applied strict criteria, looking for objects with angular motions of about three arcminutes per year and matching the expected brightness and distances predicted for Planet Nine.

Finding the Strong Candidate: A Game-Changer in the Hunt

After combing through the data, the researchers initially identified 13 candidate pairs — sources seen in both IRAS and AKARI data — showing the expected motion across the sky. These candidates corresponded to heliocentric distances between 500 and 700 AU, and masses estimated between 7 and 17 Earth masses, aligning well with theoretical predictions for Planet Nine.

Among these, one candidate emerged as particularly exciting. Visual inspection showed that the source moved between the IRAS and AKARI epochs just as expected for a distant, slow-moving object. Even more importantly, the detection probability map built from AKARI data confirmed this candidate’s behavior: appearing at two different dates and missing at others, precisely what would be expected from an object with a slow, steady orbit around the Sun.

This strong candidate stands out because it ticks multiple boxes predicted by Planet Nine models: right distance, right mass range, right speed, and independent confirmation across two sky surveys. It marks a rare convergence of evidence in a field where direct detection has remained stubbornly elusive.

The Next Steps: Why Confirmation Matters

Despite the excitement, IRAS and AKARI data alone cannot fully confirm the discovery of Planet Nine. The key challenge is that the two observations are decades apart, providing only a rough trajectory, not a precise orbit. To truly confirm that this object is orbiting the Sun — and not just a coincidental background star — astronomers need targeted follow-up observations.

The researchers propose using modern instruments like the Dark Energy Camera (DECam), a highly sensitive wide-field camera capable of spotting very faint moving objects within a few hours of exposure. By observing the candidate over several nights, astronomers can track its motion against background stars and calculate its orbit with precision.

Confirmation would be monumental: it would elevate Planet Nine from theoretical status to reality, marking the discovery of a new member of the Solar System. It would explain the odd clustering of distant trans-Neptunian objects, resolve key mysteries about the Solar System’s architecture, and force scientists to rewrite planetary formation models that have remained largely unchanged for decades.

This phase of the search — confirming and precisely tracking the candidate — is the critical next chapter that will determine whether the world finally meets its long-lost ninth planet.

The Scientific Impact: Reimagining the Solar System

Current models of planetary formation suggest that the early Solar System was a chaotic place, with planets migrating and scattering smaller bodies outward. Finding Planet Nine would support theories suggesting that a giant planet was flung into the outer darkness by gravitational interactions early in Solar System history.

Additionally, Planet Nine’s mass and orbit would influence the orbits of countless icy objects in the Kuiper Belt and beyond. Understanding its position could help map the distribution of unseen debris at the edge of our Solar System and could even hint at other unknown structures, such as distant asteroid belts or small companion worlds.

Moreover, the techniques developed in this search — combining old datasets, refining detection methods, and coordinating multi-observatory follow-ups — will set a new gold standard for how future planetary searches and distant Solar System studies are conducted.

Conclusion: A New Hope in the Planet Nine Quest

The search for Planet Nine has often felt like a cosmic treasure hunt with little more than shadows to chase. Yet now, for the first time, astronomers have a solid lead — a candidate that matches predictions and behaves just as the theoretical models said it should. While scientific caution demands that we wait for confirmation, the identification of this candidate represents the most exciting moment in the Planet Nine saga to date.

Reference:

A Search for Planet Nine with IRAS and AKARI Data