But if we've found eight (and a half) of the planets in our system already, what is making it so hard to close the book on the ninth?
They are now focusing on the thought that something beyond Neptune is present that is causing the orbits of other space objects to be affected.
While scientists are yet to directly observe this planet orbiting the Sun, what astronomers do have is enough circumstantial evidence pointing toward its existence.
They say that their finding bolsters the ever-convincing case that a so-called "Planet Nine" exists. Planet Nine, is believed to be 10 times bigger than Earth and 20 times farther out from the sun than Neptune - the outer-most planet in the solar system.
California Institute of Technology astronomer Michael Brown said there is reason to believe that if the ninth planet does exist, it could be essentially invisible to existing observatories. At that distance, the equivalent, of 600 astronomical units (1 AU is defined as the distance between the Earth and the Sun, or approximately 93 million miles), it would be 160,000 times dimmer than Neptune is.
In 2016, Caltech scientists spotted signs which offered a hint that there is a huge, unseen world lurking at the edge of our solar system - and other rocky objects have since offered hints it might be there.
Because of its vast distance from the sun and its non-reflective appearance, Planet 9 appears very dim. Researchers use Subaru's wide enviornment of peek to survey capability search plot.The efforts, nonetheless, cease no longer jabber the discovery of the planet as it'll furthermore remain hidden amid the sunshine air pollution of the Milky Technique. If Planet Nine is now at a distant point in its orbit, it could take thousands of years for it to circle back to a point where it's visible from Earth.
Another thing to consider is the wavelength of light that should be coming from Planet Nine. "It turns out that Planet Nine provides a natural avenue for their generation".
This means that our millimeter telescopes in Antarctica and Chile might be able to pick up its glow if Planet Nine happens to cross their search field.
Why cannot astronomers see the "perturber" that could be Planet number nine?