The hypothetical existence of the so-called “Planet Nine” continues to capture the attention of the international astronomical community. For years, the possibility of a massive, distant ninth planet orbiting the outer reaches of our Solar System has intrigued experts and amateurs alike, fueling one of the most exciting quests in recent space science.
Several teams have attempted to find direct signals from this mysterious celestial body. Now, recent advances have given a significant boost to research thanks to an alternative detection method: looking for the planet's own heat instead of reflected sunlight.
A different approach to a difficult-to-see planet
The team led by Amos Chen, from the National Tsing Hua University of Taiwan, has taken a step forward by applying infrared detection. They used data from the space telescope AKARI, of Japanese origin, which stands out for its ability to capture extremely weak thermal signals in the far-infrared range. This is a fundamental difference from traditional optical telescopes, which rely on light reflected from objects and are much less effective with bodies so far from the Sun.
The supposed Planet Nine would be located between 400 and 800 times farther from the Sun than Earth is, making it a real challenge for optical instruments. If it existed, it would be an ice giant, with an estimated mass between five and ten times that of Earth, and its faint glow would barely be distinguishable among thousands of distant, cold objects.
The key to the discovery lies in the fact that The thermal emission of a distant object fades much more slowly with distance than reflected light. This nuance allows instruments like AKARI to record the “ghost heat” of bodies that, for visual purposes, would be practically invisible.
Identification of two candidates and next steps
The research focused on a specific area of the sky, selected after digitally simulating the orbital patterns of objects that inhabit the Kuiper Belt, a region riddled with icy stars behind Neptune. There, the team carefully filtered out background noise—such as distant galaxies, cosmic rays, and other interference—until they found two bodies whose location and thermal brightness were similar. They coincide surprisingly with theoretical predictions for planet Nine.
The procedure involved analyzing the apparent position of these objects on different days and months. A planet so distant would move slowly in the sky, appearing almost motionless from one day to the next, but moving appreciably over long periods. After months of data comparison, only two candidates met these requirements and displayed the appropriate infrared characteristics.
Although these results do not yet constitute definitive proof – independent observations are needed to rule out other explanations and confirm its planetary nature – they surpass all previous evidence and mark the strongest progress in the recent search of this hypothetical planet.
Implications of an extraordinary discovery
Confirmation of one of these candidates as the true Planet Nine would not only add a new member to the Solar System's planetary family, but would force a review of theories about planet formation and the evolution of our cosmic environmentScientists suggest that this distant giant may have influenced the migration of other planets, the dispersal of the Kuiper Belt, and the peculiar motion of many trans-Neptunian objects.
Furthermore, it would shed light on the possible mechanisms that hide massive bodies in the outer regions of the system, unraveling part of the mystery surrounding the final architecture it adopted after its formation. Planet Nine could, in a way, be the missing piece to explain the orbital puzzle of many distant objects.
Although the mystery has not been completely solved, recent work shows that contemporary astronomy is getting closer to answering one of its greatest mysteries. The detection of heat in the sky marks a decisive step in the hunt for Planet Nine, an enigma that, perhaps in the coming years, will cease to be merely a possibility and become a reality confirmed by science.
