The hunt for the hypothetical "Planet X" has been fruitless so far, but that doesn't mean astronomers are calling it off.
A new analysis of data collected by NASA's Wide-Field Infrared Survey Explorer (WISE) spacecraft revealed no sign of the mysterious Planet X hypothesized to exist in the outer solar system. But scientists are keeping up the search for a planet or dim star far from the sun.
"I think astronomers will continue to search for a distant companion to the sun with every new, deeper survey," Kevin Luhman of the University of Pennsylvania told Space.com by email. Luhman, who studies low-mass stars and "failed stars" known as brown dwarfs, recently published the results of his search for Planet X using WISE. [Images from NASA's WISE Space Telescope]
"We have a natural desire to better determine the contents of our solar system," Luhman said. "There's a vast volume of space in the outer solar system, and we would like to know what's out there."
And a recent find may give a boost to the hunt for Planet X. On Wednesday (March 26), researchers announced they had discovered a dwarf planet orbiting the sun in a distant, largely unexplored region known as the inner Oort Cloud.
Further, the orbits of the newfound object, known as 2012 VP113, and some of its neighbors are consistent with (though by no means proof of) the existence of a planet-size "perturber" far from the sun — perhaps so distant that it cannot be detected with current instruments.
An Unseen Companion
For more than a century, astronomers have considered the possibility that another massive body exists in the outer solar system.
Percival Lowell coined the term "Planet X" at the turn of the 20th century to refer to an undiscovered large planet that could be responsible for perturbing the orbits of Uranus and Neptune. More recently, the idea grew to incorporate a possible dwarf-star companion to the sun, nicknamed "Nemesis."