Sorry, Conspiracy Theorists: Planet X Doesn't Mark the Spot

Well, that's that then. There are no other big planets in our solar system, no other giant planets orbiting the Sun in the distant, cold reaches well past Neptune. This news comes from a paper analyzing observations by WISE, the Wide-field Infrared Survey Explorer, a scrappy little mission that spent 13 months mapping the entire sky in infrared wavelengths. This is where warm objects are bright, things like dinky stars, asteroids, galactic dust, and more. WISE was very sensitive, and as able to ...