Cosmologists in Search of Planet Nine: the Case for CMB Experiments

Understand

Cosmology experiments at mm-wavelengths can detect Planet Nine if it is the size of Neptune, has an effective temperature of 40 K, and is 700 AU from the Sun.

• It would appear as a ~30 mJy source at 1 mm with an annual parallax of ~5 arcmin.
• The challenge is to distinguish it from the approximately 4000 foreground asteroids brighter than 30 mJy.
• Fortunately, these asteroids are known to the Minor Planet Center and can be identified because they move across a resolution element in a matter of hours, orders of magnitude faster than Planet Nine.