Characterising The Outer Solar System With JWST
Trams-Neptunian Objects (TNOs) are typically very small, very dark, and extremely distant. This makes it very challenging for astronomers to observe and characterise these faint cold outer solar system worlds.
This is an important task for astronomers because studies of the physical properties of TNOs are a powerful probe into the processes of solar system formation and evolution. The distant population of TNOs are seen as valuable tracers of the chemical and dynamical evolution of our solar system. Understanding the physical properties of these worlds will help us to constrain our models of solar system cosmogony, the science of solar system origin(s).
This summer's flyby of the Pluto system, and a planned future encounter with a more distant Kuiper Belt Object (KBO) by +NASA New Horizons
spacecraft has given us an unprecedented "in-situ" component to our observations that complements studies by Earth orbiting telescopes and ground-based observatories. However, it is NASA's +James Webb Space Telescope (JWST)
that promises to bring about a new era in the physical characterisation of TNOs.JWST
will provide astronomers and planetary scientists with an unprecedented capability to investigate the diverse surface compositions of these dim and distant cold worlds. When operational in 2018, this infrared space telescope will provide scientists with a wealth of data about the temperatures, diameters, albedos, and thermal properties of TNOs.
For example, JWST's MIRI instrument promises to characterise in detail the mysterious anomalous shortwave thermal emission of Makemake and Eris.
Coupling JWST observations with archival +Spitzer Space Telescope
, Herschel, and +Hubble Space Telescope
observations will refine existing data-sets and combining ALMA (radio) with JWST (infrared) offers scientists a powerful tool for studying the size, albedo, and thermal properties of the small (in diameter) TNO population, particularly the poorly understood binary TNOs.
JWST's spectral sensitivity in infrared wavelengths will allow studies of a variety of molecular ices which display spectral features in IR where optical (visible) telescopes see nothing.
Spectroscopy with NIRSpec will identify currently undetected volatiles on the surface of dwarf planets like Eris, Makemake, and Pluto, and help confirm the presence of specific volatiles like organic tholins.
Tholins are solids thought to be produced when gases in a planetary atmosphere are exposed to energetic solar/cosmic rays. These tholins are thought to be the best analog we currently have for modelling the red coloured surfaces of TNOs but there are many other chemical compounds that could potentially produce the observed red colour.
NIRSpec will readily distinguish between tholins and other chemical species like methanol, silicates, or other organics.
So once operational, JWST will be able to give us a definitive answer to the puzzling question raised by New Horizons :What is all that red stuff on Pluto and Charon ?