NASA's Wide-Field Infrared Survey Explorer (WISE) searched through hundreds of millions of objects across our sky but was unable to find any evidence of the hypothesized celestial body in our solar system commonly dubbed "Planet X."
Researchers previously had theorized about the existence of this large, but unseen celestial body, suspected to lie somewhere beyond the orbit of Pluto.
In addition to "Planet X," the body had garnered other nicknames, including "Nemesis" and "Tyche."
This recent study, which involved an examination of WISE data covering the entire sky in infrared light, found no object the size of Saturn or larger exists out to a distance of 10,000 astronomical units (au), and no object larger than Jupiter exists out to 26,000 au.
Kevin Luhman of the Center for Exoplanets and Habitable Worlds at Penn State University, University Park, Pennsylvania, said that the outer solar system probably does not contain a large gas giant planet, or a small, companion star.
The second WISE study, which concentrated on objects beyond our solar system, found 3,525 stars and brown dwarfs within 500 light-years of our Sun.
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Despite the large number of new solar neighbors found by WISE, "Planet X" did not show up. Previous speculations about this hypothesized body stemmed in part from geological studies that suggested a regular timing associated with mass extinctions on Earth.
The idea was that a large planet or small star hidden in the farthest reaches of our solar system might periodically sweep through bands of outer comets, sending them flying toward our planet. The Planet X-based mass extinction theories were largely ruled out even prior to the new WISE study.
Other theories based on irregular comet orbits had also postulated a Planet X-type body. The new WISE study now argues against these theories as well.
The study has been published in the Astrophysical Journal.