Astronomers may have found an important clue in the search for Planet Nine, a mysterious world believed to be hiding far beyond Neptune. A study published in the journal Publications of the Astronomical Society of Australia in May 2025 identified a possible Planet Nine candidate by examining old infrared telescope data.
However, researchers have not confirmed the planet’s existence, and further observations are needed to determine whether the object is truly the missing world.
What Is Planet Nine and Why Are Scientists Searching for It?
Planet Nine is a theoretical planet that may exist in the outer parts of our solar system. Scientists began examining the possibility of such a world after noticing unusual patterns in the orbits of some distant objects beyond Neptune.
Researchers believe the gravity of an undiscovered planet could help explain these patterns. According to NASA, the proposed planet could have a mass around five to ten times that of Earth and follow a long, stretched orbit around the Sun. However, its existence remains unproven, and scientists continue to debate whether it is needed to explain the observations.
How Did Astronomers Find the Possible Candidate?
The research team used data from two space telescopes: the Infrared Astronomical Satellite (IRAS) and Japan’s AKARI satellite. Their observations were made 23 years apart, giving scientists a way to look for objects that had slowly changed position over time.
Instead of searching only for reflected sunlight, the researchers examined infrared signals, which can help reveal heat from a distant object. This method could be useful because a planet so far from the Sun would be extremely difficult to spot using ordinary visible-light observations.
The team searched for matching signals in the two surveys and initially identified 13 possible pairs. After carefully checking the images and removing unsuitable candidates, they found one promising pair. The source appeared at different positions in the older IRAS observations and the later AKARI data, matching the expected movement of a distant object.
What Could the Discovery Tell Us?
The study explored a possible planet located about 500 to 700 astronomical units from the Sun. One astronomical unit is the average distance between Earth and the Sun. Based on the researchers’ models, the planet could have a mass of around seven to 17 Earth masses.
These figures are estimates used to guide the search, not confirmed measurements of a discovered planet. The team also stressed that the two sets of observations were insufficient to establish the candidate’s complete orbit. Follow-up observations are essential to check whether the signal belongs to a moving planet or another object.
Another Study Adds to the Search
A separate study, published online on May 22, 2025, also examined infrared data from AKARI. It identified two possible Planet Nine candidates whose positions and brightness matched the researchers’ predictions. The authors said both objects required further investigation before they could be confirmed.
Is Planet Nine Finally Found?
Not yet. The findings offer fresh leads, but a candidate is not the same as a confirmed planet. Astronomers must collect more observations, track the object’s movement and establish its orbit before making a firm claim.
If Planet Nine is eventually confirmed, it could transform our understanding of the solar system’s formation and structure. For now, the latest research provides a reason for renewed interest, while the biggest question remains unanswered: does this hidden planet really exist?
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