NASA's WISE Spacecraft Has Yet To Uncover Planet 'X' Beyond Pluto
While NASA's Wide-Field Infrared Survey Explorer (WISE) has uncovered thousands of new stars during its multi-year mission, it has been unable to collect any evidence supporting the supposed existence of a large but unseen celestial body believed to be located somewhere beyond Pluto's orbit.
This supposed celestial body is commonly referred to as "Planet X" -- alternatively "Nemesis" or "Tyche." However, despite the fact that the space telescope searched hundreds of millions of objects, officials from the US space agency confirmed on Friday that WISE was unable to uncover any proof that such a world actually exists.
In fact, a recent study analyzed WISE data covering the entire sky in infrared light, and found that no object at least the same size as Saturn existed within a 10,000 astronomical unit (au) distance, and that no planet at least the size of Jupiter was located within a 26,000 au distance. For reference, Earth is one au from the sun, while Pluto is roughly 40 au from the star around which it orbits, the NASA researchers noted.
"The outer solar system probably does not contain a large gas giant planet, or a small, companion star," said Kevin Luhman, an associate professor of astronomy and astrophysics at the Penn State University Center for Exoplanets and Habitable Worlds and the author of an Astrophysical Journal paper detailing the findings.
Despite the fact that WISE was unable to locate some mysterious planetoid at the edge of our solar system, a second Astrophysical Journal study reports on 3,525 new stars and brown dwarfs discovered within 500 light-years of the sun thanks to the space telescope, 762 of which had also been discovered and were catalogued as part of the Luhman study.
"We're finding objects that were totally overlooked before," said lead author Davy Kirkpatrick, a member of the NASA Infrared and Processing Analysis Center at the California Institute of Technology. He also worked on the WISE science team when it performed two scans and captured images of nearly 750 million stars, galaxies and asteroids in 2010 and early 2011.
Last November, NASA released data from the AllWISE program, allowing astronomers to compare both of the telescope's full-sky surveys in order to search for moving objects. Basically, the more an object appears to move over time in the images, the closer it is, and searches of the WISE data catalog have helped researchers uncover some of the closest stars, including a pair of brown dwarfs located just 6.5 light years away.
Despite finding a star system - the closest discovery of its kind in nearly a century - the so-called "Planet X" does not appear anywhere in the WISE sky surveys. Much of the speculation surrounding this world stems from geological studies suggesting an association with mass extinctions here on Earth, the space agency said.
"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," NASA explained.
"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 agency added. "Both of the WISE searches were able to find objects the other missed, suggesting many other celestial bodies likely await discovery in the WISE data."
Even though WISE was put into hibernation after completing its primary mission in 2011, it was reactivated and renamed NEOWISE two years later. It was also presented with a new mission: to help NASA scientists identify and learn more about potentially hazardous asteroids and other near-Earth objects.
However, even though its original primary mission may have officially concluded, UCLA professor Ned Wright, the principal investigator of the mission, believes that there is still more to learn from the instrument's sky surveys.
"We think there are even more stars out there left to find with WISE," he said. "We don't know our own sun's backyard as well as you might think."