An astronomer from Imperial College London has discovered possible planet X in old images 
Astronomer Michael Rowan-Robinson of Imperial-Robinson College London has discovered a possible candidate for the ninth planet in the solar system on old infrared images of the sky. This object can be a planet several times more massive than the Earth and several hundred astronomical units away from the Sun. The scientist published the search results in the arXiv preprint repository.
Robinson conducted the first searches for a large planet beyond the orbit of Neptune back in 1983, using the catalog of objects observed by IRAS, an infrared orbital observatory launched in 1982. His efforts led to the discovery of Comet Bowell, but no signs of the existence of a ninth planet were found. However, in recent years, scientists have suggested that a large planet could be very distant and in a highly inclined orbit.
Robinson re-searched IRAS for possible signs of a ninth planet in the solar system. They were guided by the sensitivity of a space telescope, which is able to fix a planet from five times the mass of the Earth at a distance of up to 220 astronomical units to 20 Earth masses at a distance of a thousand astronomical units. Given this range of distances, the planet should look like a point source of infrared light with a wavelength of 60 micrometers.
He found several unidentified candidate sources. Lethal analysis has shown that some of them can be identified with galaxies. Other possible sources were checked for their presence in the data, covering various periods of time, from a few hours to six months. The only suitable candidate was found that could correspond to a planet with a mass of 3-5 Earth masses, located at a distance of about 225 astronomical units.
According to Robinson, it is necessary to carry out dynamic simulations to find out whether the candidate matches the orbits of the already known objects of the solar system and whether it can explain the apparent clustering of the orbits of dwarf planets in the Kuiper belt. This clustering is currently the main evidence in favor of the possible existence of Planet X.