Astronomers track candidate signal of Planet Nine in space survey data
An international research team led by Terry Long Phan at National Tsing Hua University in Taiwan has detected a candidate infrared source that may represent the first direct observational evidence of Planet Nine. The potential detection emerged from a systematic comparison of sky survey data gathered 23 years apart by two separate infrared orbital observatories, tracking an object moving slowly across the outer edges of the Solar System.
Astrobiologist Lewis Dartnell, who reviewed the findings published in Publications of the Astronomical Society of Australia, described the significance of the signal while pointing out the preliminary nature of the work. “It’s very early days, but if this pair of faint pinpricks does in fact represent a single, slow-moving object in our Solar System, we may have just got our first observational evidence of Planet 9,” Dartnell stated.
Infrared surveys track shifting candidate over 23 years
Searching for massive celestial bodies beyond the orbit of Neptune presents steep physical hurdles when relying on standard optical telescopes. If a body with a mass between 7 and 17 Earth masses orbits the Sun at ten times the distance of Neptune, sunlight striking its surface must make a complete round trip across billions of kilometers to reach terrestrial sensors. This geometry causes a Neptune-sized object at that distance to appear 10,000 times fainter in visible light than Neptune itself. Emitted thermal radiation travels only one way from the warm interior of the planet out into deep space, which leaves the target roughly 100 times fainter in far-infrared wavelengths and makes infrared surveys the primary mechanism for direct searches.
To identify objects traveling across these extreme distances, Phan worked alongside collaborators including astrophysicist Tomotsugu Goto to cross-reference two historical sky archives separated by more than two decades. The research paired catalog records from the Infrared Astronomical Satellite, launched by an international consortium in 1983, with mapping data from the Japanese satellite AKARI, launched in 2006. Because an object located hundreds of astronomical units away moves slowly, it appears stationary in observations taken during a single satellite mission but displays measurable positional drift across several decades.
Automated algorithms isolate single candidate for Planet Nine
The research group developed automated computational filters to scan millions of point sources recorded by the two space platforms. The initial search program selected 13 candidate pairs of emissions that aligned with the slow angular velocity expected for an unmapped trans-Neptunian planet. Following this algorithmic screening, Phan performed detailed manual inspections of the raw imagery to weed out optical artifacts, background instrumental noise, and uncataloged galactic structures. After completing the verification workflow, only a single candidate pair remained viable.
The surviving candidate appears at a distinct coordinate in the 1983 IRAS survey and shifts 47.5 arcminutes in the 2006 AKARI survey, a distance equal to roughly 1.5 times the angular width of the full Moon. Crucially, the source does not exist at its 1983 coordinates in the 2006 AKARI observation data, nor does any stationary infrared emitter exist at the 2006 coordinates in the earlier 1983 IRAS plates. This absence at alternating epochs confirms that the signal behaves consistently with an individual, slow-moving celestial body within the Solar System rather than a stationary cosmic background feature.
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Key parameters of the candidate detection
- Separation period: 23 years between the IRAS mission in 1983 and the AKARI mission in 2006
- Observed angular shift: 47.5 arcminutes across the 23-year baseline
- Estimated heliocentric distance: 500 to 700 Astronomical Units from the Sun
- Modeled mass range: 7 to 17 times the mass of Earth
- Initial algorithmic candidates: 13 potential source pairs
- Verified candidate pairs remaining: 1 viable detection
Kuiper Belt alignments and orbital calculations
The hypothesis of a ninth planet gained substantial traction in 2016 when Caltech astronomers Mike Brown and Konstantin Batygin calculated that peculiar orbital clusterings and severe inclinations among distant Kuiper Belt objects stemmed from the gravitational pull of an unseen perturber. The physical models evaluated in Phan’s study set search parameters for bodies located between 500 and 700 Astronomical Units, where one Astronomical Unit equals the average distance between Earth and the Sun. At these distances, a planet’s motion over 23 years generates an expected shift between 42 and 69.6 arcminutes, fitting the observed 47.5 arcminute displacement.
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Astronomers have not confirmed whether the pair of detections constitutes a genuine physical planet or an accidental alignment of two unrelated astrophysical background sources. Two historical coordinate readings provide insufficient data points to compute an accurate Keplerian orbital path or confirm gravitational closure around the Sun. Validating the true nature of this infrared source requires targeted ground-based follow-up campaigns, with scientists pointing to the sensitive Dark Energy Camera mounted on the Victor M. Blanco Telescope in Chile as the instrument needed to track the candidate at its current projected sky position.
