NASA's WISE Survey Reveals No 'Planet X' but does Find a Wealth of New Stars

A large, unknown planet with a sweeping orbit that periodically crashes into our solar system's asteroid field does not exist, according to a new report. 

For years, astronomers have suggested that a so-called "Planet X" exists in our solar system beyond the orbit of Pluto, but after an exhaustive search that involved hundreds of millions of celestial objects, astronomers have found no evidence of of this theoretical planet. However, a wealth of previously undocumented stars were found in the search.

The search, conducted by NASA's Wide-Field Infrared Survey Explorer (WISE), involved covering the entire night sky in infrared light and scanning for celestial objects, revealed that there is no object the size of Saturn or larger in existence out to 10,000 astronomical units (AU) from Pluto. (One AU is the distance from Earth to the Sun, about 93 million miles. Pluto is about 40 AU from the Sun.)

While there could theoretically be a less-than-Saturn sized planet in the depths beyond Pluto, all theories supporting the idea of Planet X suggest that the planet is massive.

"The outer solar system probably does not contain a large gas giant planet, or a small, companion star," said Kevin Luhman of the Center for Exoplanets and Habitable Worlds at Penn State University. Luhman and his colleagues published their evidence in the Astrophysical Journal.

Although the WISE data did not reveal a Planet X, it did reveal a wealth of other information, including evidence of star systems in our solar system's relative "backyard."

These neighboring star systems, which include brown dwarfs and more active stars, have been essentially hiding in plain sight, the astronomers said.

The WISE data revealed 3,525 stars and brown dwarfs within 500 light years of the Sun.

"We're finding objects that were totally overlooked before," said Davy Kirkpatrick of NASA's Infrared and Processing Analysis Center at the California Institute of Technology. Kirkpatrick is lead author of a second paper using WISE data, also in the Astrophysical Journal.

The WISE mission, which took place between 2010 and 2011, preformed two full scans of the sky with a half-year gap in between scans. By comparing data in the scans, researchers can look for moving objects in space. Nearly 750 million asteroids, stars and galaxies were imaged by the WISE project.