Evidence suggests that the mysterious Planet Nine had already been detected in 1983

An analysis of data collected by the IRAS satellite (Infrared Astronomical Satellite) in 1983 has yielded a trio of point sources that could be the hypothetical Planet Nine. The document is available on the arXiv prepress server and has been accepted for publication in the Monthly Notices of the Royal Astronomical Society.

Planet Nine is the provisional name for a massive world that would orbit the Sun twenty times beyond Neptune. Theorized in 2016 based on the behavior of a group of trans-Neptunian objects, it has been searched unsuccessfully in several astronomical observation campaigns.

Now astronomer Michael Rowan-Robinson of Imperial College London argues that the IRAS data should encourage scientists to keep looking for this planet, Science Alert reports.

It is unlikely that it is a real detection, but the possibility means that it could be used to model where the planet now to perform a more specific search, in the future search to confirm or rule out its existence, he argues.

“Given the poor quality of IRAS detections, at the very edge of the survey, and in a very difficult part of the sky for far-infrared detections, the probability that the candidate is real is not overwhelming,” he wrote.

Later, he added: “However, given the great interest of the hypothesis of Planet nine it would be worth checking if an object with the proposed parameters and in the proposed sky region is incompatible (…) ”.

IRAS operated for 10 months, beginning in January 1983, conducting a far infrared survey of 96% of the sky. At this wavelength, small, cool objects like Planet Nine might be detectable, so Rowan-Robinson decided to re-analyze the data using consistent parameters.

Of the around 250,000 point sources detected by the satellite only three are of interest as candidates for Planet Nine. In June, July, and September 1983, the satellite detected what appears to be an object moving across the sky.

The region of the sky in which the source appears is at a low latitude in the galaxy (that is, close to the plane of the Milky Way) and is strongly affected by galactic cirrus clouds, filamentous clouds that glow in the far infrared. So it is possible that the sources are the noise from these clouds.

Rowan-Robinson also notes that another highly sensitive system, the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), in operation since 2008, has failed to recover the candidate.

However, if we interpret the candidate as real, we can extrapolate some information about Planet Nine. According to IRAS data, it would have between three and five times the mass of the Earth, at an orbital distance of around 225 astronomical units (one of them is equivalent to the space that separates our planet from the Sun).

With information from Europa Press.