Planetary Studies Through the CMB-HD Survey

The complete inventory of planets, dwarf planets, and asteroids in our own Solar System remains an open question. CMB-HD can open a new discovery space in our outer Solar System by detecting undiscovered Solar System bodies via their thermal flux and parallactic motion. Objects close to the Sun are normally detected via optical observations, which are sensitive to the bodies’ reflected light from the Sun. However, objects also have internal heat that is emitted at millimeter wavelengths. Since the flux from reflected light falls faster with distance than directly sourced emission, CMB-HD has an advantage over optical surveys in finding objects in the far Solar System. In particular, CMB-HD could detect dwarf-size planets hundreds of AU from the Sun, and Earth-sized planets thousands of AU from the Sun. In combination with optical measurements, CMB-HD would allow large population studies of the sizes and albedos of these objects. In addition, whether our Solar System, and exo-solar systems in general, possess an Oort cloud is still unknown. The low-noise and high-resolution of CMB-HD would enable the detection of exo-Oort clouds around other stars, opening a new window on planetary studies.