Researchers identify potential direct Planet Nine candidate, ZME Science reports

Astronomers hunting for Planet Nine have identified a faint infrared source that shifted across the sky over a 23-year baseline, marking a potential direct observation of the hypothetical world, ZME Science reported. The object was pulled from millions of infrared signatures in archived space telescope data, offering researchers their single best candidate after years of relying on the gravitational footprints of clustered trans-Neptunian objects.

Locating Faint Infrared Signatures Beyond Neptune

Finding a distant, massive body at the edges of the Solar System is notoriously difficult because visible sunlight struggles to reach distances hundreds of times farther from the Sun than Earth. According to findings covered by Sky at Night Magazine, a Neptune-sized planet positioned ten times further away than Neptune would appear 10,000 times fainter. However, thermal infrared radiation fades much more slowly over distance than reflected sunlight, making space-based infrared telescopes the primary tool for detection.

Terry Long Phan of National Tsing Hua University in Taiwan led a research team analyzing data from two far-infrared all-sky surveys to spot movement over time. The team compared observations from the Infrared Astronomical Satellite, which mapped the sky in 1983, and Japan’s AKARI spacecraft, which conducted subsequent infrared surveys in 2006 and 2007. Because a distant planet moves extremely slowly from night to night, the 23-year gap between the two missions provided a long enough baseline for a slow-moving object to visibly drift across the sky.

Filtering Million-Source Datasets Down to One Target

The researchers filtered more than one million sources from each survey based on brightness, location, and infrared characteristics to isolate potential candidates. That filtering process initially produced 22 possible pairings before additional checks trimmed the count to 13. Visual inspection of those remaining targets left just one single source that matched the expected profile of a planet between 500 and 700 astronomical units from the Sun with a mass roughly 7 to 17 times that of Earth. ZME Science noted that the candidate shifted by 47.46 arcminutes between the 1983 IRAS observations and the 2006-2007 AKARI detections, which is about one and a half times the apparent width of the full Moon.

Despite the positional shift, the researchers stress that they have not definitively discovered Planet Nine. Sky at Night Magazine reported that knowing only two positions separated by decades is insufficient to calculate a reliable orbit. One of the candidate's AKARI infrared measurements appears unusually faint and could be unreliable, while the entire search methodology relied on specific assumptions regarding the planet's mass, temperature, density, and distance.

Targeting Follow-Up Observations at the Blanco Telescope

To confirm whether the object is a true Solar System planet or a false lead, Phan and his colleagues have proposed pointing the Dark Energy Camera on the 4-meter Blanco Telescope in Chile at the target area. Additional imaging will reveal whether the faint point of light continues along a planetary orbit or vanishes from view. Until those follow-up observations are completed and an orbit is verified, Planet Nine remains strictly hypothetical, though astronomers now have a tangible point in the night sky to investigate.