for the James Webb Space Telescope
Astronomers have known for some time that objects in the distant Kuiper Belt region of the solar system, whether small debris or large objects like Pluto and its moons, contain icy surfaces. The New Horizons flyby of 2015 captured Pluto’s icy surfaces in great detail, revealing them to be much more dynamic than originally expected. Even still, a good inventory of the ices present in the outer solar system has yet to be taken, and the evolution of the surface features remains poorly understood. It is as yet unknown whether these objects have fresh icy surfaces, perhaps resulting from damaged ices knocked off during a collision, or much older icy surfaces modified by cosmic rays and ultraviolet light from the sun. Both can cause chemical reactions, resulting in a darkening in color, as can be seen on objects throughout the Kuiper Belt region.
Increasing our understanding of the formation process and surface composition of Kuiper Belt Objects (KBOs), such as possible collisions, or correlations between KBO orbits and their surface properties, will provide new insight into the formation processes of the early solar system. Understanding these formation processes requires attention to both large and small KBOs alike. While the biggest, brightest objects in the Kuiper Belt will be prime targets for the NIRSpec instrument, NIRCam will be used to observe fainter KBOs, such as those with dark, less reflective surfaces, or KBOs defining the small end of size distributions.
Studying surface ices of KBOs may also prove useful to exoplanet astronomers seeking to understand the formation and evolution of planetary systems other than our own. With NIRCam, astronomers may be able to relate ices found on KBOs to ices found on dust grains of exo-solar systems or in dust clouds around newly forming stars. The following plot shows the reflectance as a function of wavelength for three likely ices along with transmission plots for the medium filters in NIRCam that would be used to study them. Read more about NIRCam’s medium filters on the Filters page.
KBO spectral energy distrubtions (SEDs) can be measured with JWST, as illustrated in the plot below. The diamonds show 10-sigma detections using NIRCam and MIRI for 10,000 per filter. The hypothetical KBO is at a distance of 45 AU, has a diameter of 200 km, and an albedo of 0.10.