The ninth planet - a hypothetical planet in the outer solar system that may be hiding beyond the orbit of Neptune - was never found in the result of research that lasted six years. It is reported by LiveScience with reference to a publication in The Astrophysical Journal. Astronomers analyzed observations made by the Atacama Telescope (ACT) in Chile, which covered about 87% of the sky visible from the Southern Hemisphere.
Astronomers have been able to identify over 3,000 potential light sources located at a distance of 400 to 800 astronomical units (AU), which could be the Ninth planet, but with a closer study, expectations did not materialize. However, failure does not in itself disprove the existence of such a planet, but rather narrows the scope of places where it can hide, and its properties.
The search began in 2016, 10 years after Pluto lost its title as the ninth planet in the solar system, as astronomers downgraded it to an ordinary dwarf planet. Scientists have noticed that six rocky objects beyond the orbit of Neptune are grouped in a strange way, and this can be explained by the gravitational pull of an invisible planet, which is five to ten times the size of Earth. The biggest problem in hunting Planet Nine is distance. If Pluto is at 30-50 AU from the Sun, then the Ninth planet is between 400-800 AU. This distance is so great that sunlight may not reach the planet at all.
All this does not leave hope that the Ninth planet can be detected using standard visible light telescopes. However, more sensitive equipment, such as the millimeter telescope at the Simons Observatory, which is being built in the Atacama Desert in Chile, can help. Such a telescope is capable of exploring space at millimeter wavelengths, a short form of radio waves that approach infrared radiation.