01-21-2016, 01:09 AM
Hmm, I'm giving the star theory very slightly more credence since I didn't realize brown dwarfs could emit light below the visible spectrum (infared). However, NASA has scanned the entire sky with an instrument designed specifically to scan the sky for brown dwarfs. They mention this in the article I linked:
Quote:At first blush, another potential problem comes from NASA’s Widefield Infrared Survey Explorer (WISE), a satellite that completed an all-sky survey looking for the heat of brown dwarfs—or giant planets. It ruled out the existence of a Saturn-or-larger planet as far out as 10,000 AU, according to a 2013 study by Kevin Luhman, an astronomer at Pennsylvania State University, University Park. But Luhman notes that if Planet X is Neptune-sized or smaller, as Batygin and Brown say, WISE would have missed it. He says there is a slim chance of detection in another WISE data set at longer wavelengths—sensitive to cooler radiation—which was collected for 20% of the sky. Luhman is now analyzing those data.