Taiwan believes it has found the mythical planet 9 of the solar system by searching for its heat instead of its light

Numerous failed attempts to find Planet 9—a hypothetical gas giant at the edge of our solar system—have led Taiwanese scientists to rethink their strategy.

For years, astronomers have scanned the sky searching for faint sunlight reflecting off Planet 9, but this method has not been successful.

Now, a team of researchers from Taiwan has adopted a different approach: instead of looking for its light, they are searching for its heat. This strategy is showing promising results, as they have identified two strong candidates.

Beyond Neptune lies the cold and dark Kuiper Belt, where the orbits of several objects appear to cluster in an unusual way. It seems as though an invisible force is influencing their movements.

One possible explanation is the existence of a massive, unknown planet—Planet 9. If it exists, it would have a mass five to ten times greater than Earth’s. However, it would also be extremely distant, more than 400 times the distance between the Earth and the Sun, making its reflected light incredibly faint.

The team from Taiwan believes they may have found the strongest evidence yet for the existence of Planet 9. Their study has produced two very promising candidates.

Any object with a temperature above absolute zero emits thermal radiation—essentially heat. While reflected sunlight diminishes with distance much faster, thermal radiation fades more slowly. This difference led the researchers to focus on the planet’s heat signature instead of its light.

The researchers analyzed data from Japan’s AKARI space telescope, which was launched in 2006. This telescope mapped the sky in far-infrared light, making it ideal for detecting the faint thermal glow of a distant object like Planet 9.

Starting with a list of more than five million signals, they narrowed down the candidates by focusing on specific areas of the sky, removing known objects, filtering out signals affected by cosmic dust, and eliminating stationary sources that did not show the expected motion.

This process reduced the list to 393 candidates. From there, they carefully examined each one, discarding weak detections, image artifacts, and other false positives.

In the end, only two candidates remained. These two heat sources appeared exactly where Planet 9 is expected to be, with the right brightness and the predicted motion. They stayed in place over a 24-hour period but disappeared from view six months later, as expected for a distant, moving object.

The two candidates have been named FISSSDL J0250422-15011 and FISSSDL J0301112-164240. To confirm whether they are indeed Planet 9, follow-up observations are needed, using powerful telescopes that can detect their faint optical light and accurately track their movement.

If confirmed, this discovery would not only solve one of astronomy’s greatest mysteries but also transform our understanding of the solar system’s formation and evolution. While nothing is certain yet, scientists now have a promising lead to follow.