The first driver for the design of POLLUX is to take advantage of the large collecting power of LUVOIR -- providing a sensitivity threshold raised by a factor of 10 to 25 with respect to Hubble in the UV --, of its pointing stability and very dark background, to operate on a broad spectral range (90 to 400 nm), at very high spectral resolution (R = 120,000). These two specificities are mandatory to probe the thousands of atomic and molecular transitions of most of the chemical species in the Universe, uniquely available in the space UV band. This will allow to follow the life cycle of matter over cosmic time, from galaxies forming stars out of interstellar gas and grains, and stars forming planets, to the various forms of feedback into the interstellar and intergalactic medium (ISM and IGM), including black hole accretion disks in active galactic nuclei (AGN).
The most innovative characteristic of POLLUX is its unique spectropolarimetric capability that will enable detection of the UV polarized light reflected from
exoplanets or from their circumplanetary material, and moons, and characterization of the magnetospheres of stars and planets, and their interactions. Observations of planets in
the solar system with POLLUX will be complementary to in situ observations, as they will inform us on the magnetospheric properties with the same levels of detail, but further
provide a long-term survey capability. The influence of magnetic fields on the Galactic scale and in the IGM will be measured. UV circular and linear polarization will provide a
full picture of magnetic field properties and impact for a variety of media and objects, from AGN jets to all types of stars. Linear polarimetry is especially powerful to provide
information on deviations from spherical symmetry, providing an extension of interferometry into a domain that is not restricted by the angular size of the objects but by their flux.
This aspect of POLLUX will be a very powerful tool for studies of the physics and large-scale structure of accretion disks around young stars and white dwarfs, or supermassive black
holes in AGNs, and to constrain the properties of stellar ejecta and explosions.
Since the parameter space opened by POLLUX is essentially uncharted territory, its potential for groundbreaking discoveries is tremendous. It will also neatly complement and enrich some of the cases advanced for LUMOS, the multi-object UV spectrograph for LUVOIR. In the links below we outline a selection of key science topics driving the POLLUX design.